Add project files.

rusnova/wwwroot/lib/twitter-bootstrap/scss/mixins/_transition.scss

@@ -0,0 +1,26 @@
+// stylelint-disable property-disallowed-list
+@mixin transition($transition...) {
+  @if length($transition) == 0 {
+    $transition: $transition-base;
+  }
+
+  @if length($transition) > 1 {
+    @each $value in $transition {
+      @if $value == null or $value == none {
+        @warn "The keyword 'none' or 'null' must be used as a single argument.";
+      }
+    }
+  }
+
+  @if $enable-transitions {
+    @if nth($transition, 1) != null {
+      transition: $transition;
+    }
+
+    @if $enable-reduced-motion and nth($transition, 1) != null and nth($transition, 1) != none {
+      @media (prefers-reduced-motion: reduce) {
+        transition: none;
+      }
+    }
+  }
+}