Add v5.1.0 docs (#34675)

docs/5.1/examples/dropdowns/dropdowns.css

@@ -0,0 +1,89 @@
+.b-example-divider {
+  height: 3rem;
+  background-color: rgba(0, 0, 0, .1);
+  border: solid rgba(0, 0, 0, .15);
+  border-width: 1px 0;
+  box-shadow: inset 0 .5em 1.5em rgba(0, 0, 0, .1), inset 0 .125em .5em rgba(0, 0, 0, .15);
+}
+
+.bi {
+  vertical-align: -.125em;
+  fill: currentColor;
+}
+
+.dropdown-menu {
+  position: static;
+  display: block;
+  width: auto;
+  margin: 4rem auto;
+}
+
+.dropdown-menu-macos {
+  display: grid;
+  gap: .25rem;
+  padding: .5rem;
+  border-radius: .5rem;
+}
+.dropdown-menu-macos .dropdown-item {
+  border-radius: .25rem;
+}
+
+.dropdown-item-danger {
+  color: var(--bs-red);
+}
+.dropdown-item-danger:hover,
+.dropdown-item-danger:focus {
+  color: #fff;
+  background-color: var(--bs-red);
+}
+.dropdown-item-danger.active {
+  background-color: var(--bs-red);
+}
+
+.btn-hover-light {
+  text-align: left;
+  background-color: var(--bs-white);
+  border-radius: .25rem;
+}
+.btn-hover-light:hover,
+.btn-hover-light:focus {
+  color: var(--bs-blue);
+  background-color: var(--bs-light);
+}
+
+.cal-month,
+.cal-days,
+.cal-weekdays {
+  display: grid;
+  grid-template-columns: repeat(7, 1fr);
+  align-items: center;
+}
+.cal-month-name {
+  grid-column-start: 2;
+  grid-column-end: 7;
+  text-align: center;
+}
+.cal-weekday,
+.cal-btn {
+  display: flex;
+  flex-shrink: 0;
+  align-items: center;
+  justify-content: center;
+  height: 3rem;
+  padding: 0;
+}
+.cal-btn:not([disabled]) {
+  font-weight: 500;
+}
+.cal-btn:hover,
+.cal-btn:focus {
+  background-color: rgba(0, 0, 0, .05);
+}
+.cal-btn[disabled] {
+  opacity: .5;
+}
+
+.form-control-dark {
+  background-color: rgba(255, 255, 255, .05);
+  border-color: rgba(255, 255, 255, .15);
+}