v5.2.0 design refresh, plus responsive offcanvas classes (#35736)

* Add responsive offcanvas classes

- Updates navbar-expand classes to de-dupe some styles—these shouldn't interfere now.
- Adds some JS to the offcanvas component to help with responsiveness

Co-Authored-By: GeoSot <geo.sotis@gmail.com>

* Redesign homepage, docs, and examples

Homepage:

- New Bootstrap purple navbar
- Redesigned masthead
- Rewrote and redesigned homepage content
- Replace Copy text with icons like Bootstrap Icons site across all ClipboardJS instances
- Fixed padding issues in site footer
- Match homepage button styles to examples page, use gap instead of tons of responsive margin utils

Docs:

- New navbar, no more subnav. Migrated search and version picker into the main navbar and refreshed the design of it all, including the responsive toggles.
- New sidebar navigation is always expanded, and now features Bootstrap Icons alongside section headings
- Sidebar navigation autoscrolls to active link for better usability
- Subnav and navbar padding issues ironed out
- Enhanced the version picker in anticipation of v5.2: we can now link right to the same page in the previous version.
- Redesign callouts to add more color to our pages
- Collapse table of contents on mobile
- Cleanup and redesign button styles with CSS variables
- Update design for subnav version dropdown
- Update highlight and example to be full-width until md
- Improve the Added In badges
- Turn the ToC into a well on mobile
- Redesign code snippets to better house two action buttons

Examples:

- Redesign Examples page layout
- Add new example for responsive offcanvases in navbars

* Convert offcanvas to CSS vars

* Feat: add resize handler to Offcanvas.js.

If we could use as default the `.offcanvas` class without modifiers, we then, could add a simplified selector
The selector itself, ignores the .offcanvas class as it doesn't have any responsive behavior
The `aria-modal` addon is to protect us, selection backdrop elements

* Separate examples code, Add some selectors, fix stackblitz btn

Co-authored-by: GeoSot <geo.sotis@gmail.com>

scss/_navbar.scss

@@ -222,41 +222,31 @@
           display: none;
         }
 
-        .offcanvas-header {
-          display: none;
-        }
-
         .offcanvas {
-          position: inherit;
-          bottom: 0;
+          // stylelint-disable declaration-no-important
+          position: static;
           z-index: auto;
           flex-grow: 1;
-          visibility: visible !important; // stylelint-disable-line declaration-no-important
-          background-color: transparent;
-          border-right: 0;
-          border-left: 0;
+          width: auto !important;
+          height: auto !important;
+          visibility: visible !important;
+          background-color: transparent !important;
+          border: 0 !important;
+          transform: none !important;
           @include box-shadow(none);
           @include transition(none);
-          transform: none;
-        }
-        .offcanvas-top,
-        .offcanvas-bottom {
-          height: auto;
-          border-top: 0;
-          border-bottom: 0;
-        }
+          // stylelint-enable declaration-no-important
 
-        .offcanvas-body {
-          display: flex;
-          flex-grow: 0;
-          padding: 0;
-          overflow-y: visible;
-        }
+          .offcanvas-header {
+            display: none;
+          }
 
-        // Reset `background-color` in case `.bg-*` classes are used in offcanvas
-        .offcanvas,
-        .offcanvas-body {
-          background-color: transparent !important; // stylelint-disable-line declaration-no-important
+          .offcanvas-body {
+            display: flex;
+            flex-grow: 0;
+            padding: 0;
+            overflow-y: visible;
+          }
         }
       }
     }

scss/_offcanvas.scss

@@ -1,27 +1,115 @@
-.offcanvas {
-  position: fixed;
-  bottom: 0;
-  z-index: $zindex-offcanvas;
-  display: flex;
-  flex-direction: column;
-  max-width: 100%;
-  color: $offcanvas-color;
-  visibility: hidden;
-  background-color: $offcanvas-bg-color;
-  background-clip: padding-box;
-  outline: 0;
-  @include box-shadow($offcanvas-box-shadow);
-  @include transition(transform $offcanvas-transition-duration ease-in-out);
+// stylelint-disable function-disallowed-list
 
-  &.showing,
-  &.show:not(.hiding) {
-    transform: none;
+%offcanvas-css-vars {
+  // scss-docs-start offcanvas-css-vars
+  --#{$prefix}offcanvas-width: #{$offcanvas-horizontal-width};
+  --#{$prefix}offcanvas-height: #{$offcanvas-vertical-height};
+  --#{$prefix}offcanvas-padding-x: #{$offcanvas-padding-x};
+  --#{$prefix}offcanvas-padding-y: #{$offcanvas-padding-y};
+  --#{$prefix}offcanvas-color: #{$offcanvas-color};
+  --#{$prefix}offcanvas-bg: #{$offcanvas-bg-color};
+  --#{$prefix}offcanvas-border-width: #{$offcanvas-border-width};
+  --#{$prefix}offcanvas-border-color: #{$offcanvas-border-color};
+  --#{$prefix}offcanvas-box-shadow: #{$offcanvas-box-shadow};
+  // scss-docs-end offcanvas-css-vars
+}
+
+@each $breakpoint in map-keys($grid-breakpoints) {
+  $next: breakpoint-next($breakpoint, $grid-breakpoints);
+  $infix: breakpoint-infix($next, $grid-breakpoints);
+
+  .offcanvas#{$infix} {
+    @extend %offcanvas-css-vars;
   }
+}
 
-  &.showing,
-  &.hiding,
-  &.show {
-    visibility: visible;
+@each $breakpoint in map-keys($grid-breakpoints) {
+  $next: breakpoint-next($breakpoint, $grid-breakpoints);
+  $infix: breakpoint-infix($next, $grid-breakpoints);
+
+  .offcanvas#{$infix} {
+    @include media-breakpoint-down($next) {
+      position: fixed;
+      bottom: 0;
+      z-index: $zindex-offcanvas;
+      display: flex;
+      flex-direction: column;
+      max-width: 100%;
+      color: var(--#{$prefix}offcanvas-color);
+      visibility: hidden;
+      background-color: var(--#{$prefix}offcanvas-bg);
+      background-clip: padding-box;
+      outline: 0;
+      @include box-shadow(var(--#{$prefix}offcanvas-box-shadow));
+      @include transition(transform $offcanvas-transition-duration ease-in-out);
+
+      &.showing,
+      &.show:not(.hiding) {
+        transform: none;
+      }
+
+      &.showing,
+      &.hiding,
+      &.show {
+        visibility: visible;
+      }
+
+      &.offcanvas-start {
+        top: 0;
+        left: 0;
+        width: var(--#{$prefix}offcanvas-width);
+        border-right: var(--#{$prefix}offcanvas-border-width) solid var(--#{$prefix}offcanvas-border-color);
+        transform: translateX(-100%);
+      }
+
+      &.offcanvas-end {
+        top: 0;
+        right: 0;
+        width: var(--#{$prefix}offcanvas-width);
+        border-left: var(--#{$prefix}offcanvas-border-width) solid var(--#{$prefix}offcanvas-border-color);
+        transform: translateX(100%);
+      }
+
+      &.offcanvas-top {
+        top: 0;
+        right: 0;
+        left: 0;
+        height: var(--#{$prefix}offcanvas-height);
+        max-height: 100%;
+        border-bottom: var(--#{$prefix}offcanvas-border-width) solid var(--#{$prefix}offcanvas-border-color);
+        transform: translateY(-100%);
+      }
+
+      &.offcanvas-bottom {
+        right: 0;
+        left: 0;
+        height: var(--#{$prefix}offcanvas-height);
+        max-height: 100%;
+        border-top: var(--#{$prefix}offcanvas-border-width) solid var(--#{$prefix}offcanvas-border-color);
+        transform: translateY(100%);
+      }
+    }
+
+    @if not ($infix == "") {
+      @include media-breakpoint-up($next) {
+        --#{$prefix}offcanvas-height: auto;
+        --#{$prefix}offcanvas-border-width: 0;
+        background-color: transparent !important; // stylelint-disable-line declaration-no-important
+
+        .offcanvas-header {
+          display: none;
+        }
+
+        .offcanvas-body {
+          display: flex;
+          flex-grow: 0;
+          padding: 0;
+          overflow-y: visible;
+          // Reset `background-color` in case `.bg-*` classes are used in offcanvas
+          background-color: transparent !important; // stylelint-disable-line declaration-no-important
+        }
+      }
+    }
   }
 }
 
@@ -33,13 +121,13 @@
   display: flex;
   align-items: center;
   justify-content: space-between;
-  padding: $offcanvas-padding-y $offcanvas-padding-x;
+  padding: var(--#{$prefix}offcanvas-padding-y) var(--#{$prefix}offcanvas-padding-x);
 
   .btn-close {
-    padding: ($offcanvas-padding-y * .5) ($offcanvas-padding-x * .5);
-    margin-top: $offcanvas-padding-y * -.5;
-    margin-right: $offcanvas-padding-x * -.5;
-    margin-bottom: $offcanvas-padding-y * -.5;
+    padding: calc(var(--#{$prefix}offcanvas-padding-y) * .5) calc(var(--#{$prefix}offcanvas-padding-x) * .5);
+    margin-top: calc(var(--#{$prefix}offcanvas-padding-y) * -.5);
+    margin-right: calc(var(--#{$prefix}offcanvas-padding-x) * -.5);
+    margin-bottom: calc(var(--#{$prefix}offcanvas-padding-y) * -.5);
   }
 }
 
@@ -50,41 +138,6 @@
 
 .offcanvas-body {
   flex-grow: 1;
-  padding: $offcanvas-padding-y $offcanvas-padding-x;
+  padding: var(--#{$prefix}offcanvas-padding-y) var(--#{$prefix}offcanvas-padding-x);
   overflow-y: auto;
 }
-
-.offcanvas-start {
-  top: 0;
-  left: 0;
-  width: $offcanvas-horizontal-width;
-  border-right: $offcanvas-border-width solid $offcanvas-border-color;
-  transform: translateX(-100%);
-}
-
-.offcanvas-end {
-  top: 0;
-  right: 0;
-  width: $offcanvas-horizontal-width;
-  border-left: $offcanvas-border-width solid $offcanvas-border-color;
-  transform: translateX(100%);
-}
-
-.offcanvas-top {
-  top: 0;
-  right: 0;
-  left: 0;
-  height: $offcanvas-vertical-height;
-  max-height: 100%;
-  border-bottom: $offcanvas-border-width solid $offcanvas-border-color;
-  transform: translateY(-100%);
-}
-
-.offcanvas-bottom {
-  right: 0;
-  left: 0;
-  height: $offcanvas-vertical-height;
-  max-height: 100%;
-  border-top: $offcanvas-border-width solid $offcanvas-border-color;
-  transform: translateY(100%);
-}

scss/_spinners.scss

@@ -29,7 +29,7 @@
   --#{$prefix}spinner-animation-name: spinner-border;
   // scss-docs-end spinner-border-css-vars
 
-  border: var(--#{$prefix}spinner-border-width) solid currentColor;
+  border: var(--#{$prefix}spinner-border-width) solid currentcolor;
   border-right-color: transparent;
 }