Bootstrap5 (#17)

* Bootstrap5 migration

dev/scss/bootstrap/helpers/_clearfix.scss

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+.clearfix {
+  @include clearfix();
+}

dev/scss/bootstrap/helpers/_colored-links.scss

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+@each $color, $value in $theme-colors {
+  .link-#{$color} {
+    color: $value;
+
+    @if $link-shade-percentage != 0 {
+      &:hover,
+      &:focus {
+        color: if(color-contrast($value) == $color-contrast-light, shade-color($value, $link-shade-percentage), tint-color($value, $link-shade-percentage));
+      }
+    }
+  }
+}

dev/scss/bootstrap/helpers/_position.scss

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+// Shorthand
+
+.fixed-top {
+  position: fixed;
+  top: 0;
+  right: 0;
+  left: 0;
+  z-index: $zindex-fixed;
+}
+
+.fixed-bottom {
+  position: fixed;
+  right: 0;
+  bottom: 0;
+  left: 0;
+  z-index: $zindex-fixed;
+}
+
+// Responsive sticky top
+@each $breakpoint in map-keys($grid-breakpoints) {
+  @include media-breakpoint-up($breakpoint) {
+    $infix: breakpoint-infix($breakpoint, $grid-breakpoints);
+
+    .sticky#{$infix}-top {
+      position: sticky;
+      top: 0;
+      z-index: $zindex-sticky;
+    }
+  }
+}

dev/scss/bootstrap/helpers/_ratio.scss

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+// Credit: Nicolas Gallagher and SUIT CSS.
+
+.ratio {
+  position: relative;
+  width: 100%;
+
+  &::before {
+    display: block;
+    padding-top: var(--#{$variable-prefix}aspect-ratio);
+    content: "";
+  }
+
+  > * {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+  }
+}
+
+@each $key, $ratio in $aspect-ratios {
+  .ratio-#{$key} {
+    --#{$variable-prefix}aspect-ratio: #{$ratio};
+  }
+}

dev/scss/bootstrap/helpers/_stretched-link.scss

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+//
+// Stretched link
+//
+
+.stretched-link {
+  &::#{$stretched-link-pseudo-element} {
+    position: absolute;
+    top: 0;
+    right: 0;
+    bottom: 0;
+    left: 0;
+    z-index: $stretched-link-z-index;
+    content: "";
+  }
+}

dev/scss/bootstrap/helpers/_text-truncation.scss

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+//
+// Text truncation
+//
+
+.text-truncate {
+  @include text-truncate();
+}

dev/scss/bootstrap/helpers/_visually-hidden.scss

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+//
+// Visually hidden
+//
+
+.visually-hidden,
+.visually-hidden-focusable:not(:focus):not(:focus-within) {
+  @include visually-hidden();
+}