Adding upstream version 5.2.3+dfsg.

Signed-off-by: Daniel Baumann <daniel@debian.org>

scss/helpers/_clearfix.scss

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

scss/helpers/_color-bg.scss

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+// stylelint-disable function-name-case
+
+// All-caps `RGBA()` function used because of this Sass bug: https://github.com/sass/node-sass/issues/2251
+@each $color, $value in $theme-colors {
+  $color-rgb: to-rgb($value);
+  .text-bg-#{$color} {
+    color: color-contrast($value) if($enable-important-utilities, !important, null);
+    background-color: RGBA($color-rgb, var(--#{$prefix}bg-opacity, 1)) if($enable-important-utilities, !important, null);
+  }
+}

scss/helpers/_colored-links.scss

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+@each $color, $value in $theme-colors {
+  .link-#{$color} {
+    color: $value !important; // stylelint-disable-line declaration-no-important
+
+    @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)) !important; // stylelint-disable-line declaration-no-important
+      }
+    }
+  }
+}

scss/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 and bottom
+@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: $zindex-sticky;
+    }
+
+    .sticky#{$infix}-bottom {
+      position: sticky;
+      bottom: 0;
+      z-index: $zindex-sticky;
+    }
+  }
+}

scss/helpers/_ratio.scss

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

scss/helpers/_stacks.scss

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+// scss-docs-start stacks
+.hstack {
+  display: flex;
+  flex-direction: row;
+  align-items: center;
+  align-self: stretch;
+}
+
+.vstack {
+  display: flex;
+  flex: 1 1 auto;
+  flex-direction: column;
+  align-self: stretch;
+}
+// scss-docs-end stacks

scss/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: "";
+  }
+}

scss/helpers/_text-truncation.scss

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

scss/helpers/_visually-hidden.scss

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

scss/helpers/_vr.scss

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+.vr {
+  display: inline-block;
+  align-self: stretch;
+  width: 1px;
+  min-height: 1em;
+  background-color: currentcolor;
+  opacity: $hr-opacity;
+}