Add dark mode support (#35857)

* Add dark mode to docs

* Minor fix: missing space indentation

* Minor fix: revert utilities/z-index added-in modification

* Remove prev: and next: from doc because extracted to another PR

* Use .bg-body-tertiary in all Utilities > Overflow examples

* fix example

* Fix up spacing examples

* Update box-shadow Sass variables and utilities to auto-adjust to color modes

* Remove unused docs class

* Refactor form styles to use CSS variable for background images on .form-check and .form-switch

* Fix docs selector

* Rename shortcut for clarity

* Heading consistency

* Reintroduce missing 4th grid item in Utilities > Spacing example

* Fix bundlewatch

* .bd-callout* rendering is OK so removing comments in the code

* Update scss/_utilities.scss

Co-authored-by: Julien Déramond <julien.deramond@orange.com>

* Fix gutters example styling

* Fix text colors on background utils docs

* redesign and fix up position marker example, which doesn't show nicely in darkmode but at least isn't broken

* fix some color utils examples

* Deprecate mixin notice

* Deprecate notice for list-group-item-variant() mixin

* Revamp new link CSS vars

* Use map-keys in some each Sass files

* Remove list-group-item-variant mixin ref in sass loop desc

* Display CSS vars scoped to our built-in dark mode

* Revert previous commit

* Fix list group variant link

* Fix typo

* Remove imports of alert/list-group mixins in scss/_mixins.scss

* Small formatting + comments removal in scss/_content.scss

* Fix alert links colors

* fix dropdown border-radius mixin

* fix link color and underline again, this time using CSS var override for color var and fallback value for the underline

* fix colors on docs navbar for dark mode

* remove two changes

* missing ref

* another link underline fix, just use sass vars for link decoration for now

* missing color bg docs, plus move dropdown override to scss

* more changes from review

* fix some examples, drop unused docs navbar styles, update docs navbar color mode to use mixin

* Few fixes around type

- Restored CSS variable for color on headings, this time with a fallback value
- In conjunction, restored and wrapped the default CSS var with a null value check
- Split headings and paragraphs docs in Reboot, elaborated on them

* Restyle custom details > summary element in docs

* Rewrite some migration docs

* fix form checks

* Fix up some navbar styling, tweak docs callout

* Fix select images, mostly for validation styling

* Clean up some migration notes, document some new form control CSS vars, mention new variables-dark in sass docs

* Update site/content/docs/5.2/components/scrollspy.md

Co-authored-by: Julien Déramond <julien.deramond@orange.com>

* Apply suggestions from code review

Co-authored-by: Julien Déramond <julien.deramond@orange.com>

* mention form control css vars in migration guide

* Tweak grid and flex docs background examples

* clarify some docs

* fix some more things

Co-authored-by: Julien Déramond <juderamond@gmail.com>
Co-authored-by: Julien Déramond <julien.deramond@orange.com>

site/layouts/shortcodes/added-in.html

@@ -2,4 +2,4 @@
 
 {{- $version := .Get 0 -}}
 
-<small class="d-inline-flex mb-3 px-2 py-1 fw-semibold text-success bg-success bg-opacity-10 border border-success border-opacity-10 rounded-2">Added in v{{ $version }}</small>
+<small class="d-inline-flex mb-3 px-2 py-1 fw-semibold text-success-emphasis bg-success-subtle border border-success-subtle rounded-2">Added in v{{ $version }}</small>

site/layouts/shortcodes/callout-deprecated-dark-variants.html

@@ -0,0 +1,9 @@
+{{- /* Outputs message about dark mode component variants being deprecated in v5.3. */ -}}
+
+{{- $component := .Get 0 -}}
+
+<div class="bd-callout bd-callout-warning">
+  <p>
+    <strong>Heads up!</strong> Dark variants for components were deprecated in v5.3.0 with the introduction of color modes. Instead of adding <code>.{{ $component }}-dark</code>, set <code>data-bs-theme="dark"</code> on the root element, a parent wrapper, or the component itself.
+  </p>
+</div>

site/layouts/shortcodes/deprecated-in.html

@@ -0,0 +1,5 @@
+{{- /* Outputs badge to identify the version something was deprecated */ -}}
+
+{{- $version := .Get 0 -}}
+
+<small class="d-inline-flex mb-3 px-2 py-1 fw-semibold text-warning-emphasis bg-warning-subtle border border-warning-subtle rounded-2">Deprecated in v{{ $version }}</small>

site/layouts/shortcodes/example.html

@@ -28,7 +28,7 @@
 
   {{- if eq $show_markup true -}}
     {{- if eq $show_preview true -}}
-      <div class="d-flex align-items-center highlight-toolbar bg-light ps-3 pe-2 py-1">
+      <div class="d-flex align-items-center highlight-toolbar ps-3 pe-2 py-1">
         <small class="font-monospace text-muted text-uppercase">{{- $lang -}}</small>
         <div class="d-flex ms-auto">
           <button type="button" class="btn-edit text-nowrap"{{ with $stackblitz_add_js }} data-sb-js-snippet="{{ $stackblitz_add_js }}"{{ end }} title="Try it on StackBlitz">