feat(list.each()): add mixin.

Author: sciborrudnicki

src/lib/_index.scss

@@ -16,7 +16,7 @@
 // Other.
 @forward "list.add.function";
 @forward "list.append.function";
-// @forward "list.each.mixin";
+@forward "list.each.mixin";
 @forward "list.empty.function";
 @forward "list.extract-map.function";
 @forward "list.first.function";

src/lib/_list.each.mixin.scss

@@ -0,0 +1,24 @@
+// Sass.
+@use 'sass:list';
+
+// Todo
+// The `list.each()` mixin uses flow control `@each` to iterate `$list`.
+// @param `$list` A list to iterate.
+// @param `$comma` If `true` then force to iterate comma-separated list, by adding space-separated list into comma-separated.
+// @param `$index`
+@mixin each($list, $comma: true, $index: 1) {
+  @each $element in if($comma, if(list.separator($list) == space, ($list,), $list), $list) {
+    @content($element, $index);
+
+    $index: $index + 1;
+  }
+}
+
+// Examples.
+// @include each((a, b, c, d, e)) using($value) {
+//   @debug $value;
+// }
+
+// @include each((a b c d e), true) using($value) {
+//   @debug $value;
+// }