Remove unused image-url mixin. Remove rarely used tags from reset.

assets/sass/_init.scss

@@ -15,6 +15,5 @@
 @import 'mixins/clearfix/clearfix';
 @import 'mixins/debug/debug';
 @import 'mixins/flex-calc/flex-calc';
-@import 'mixins/image-url/image-url';
 @import 'mixins/rtl/rtl';
 @import 'mixins/spacing/spacing';

assets/sass/_reset.scss

@@ -85,29 +85,3 @@ kbd,
 samp {
   font-family: var(--ff-monospace);
 }
-
-// Mark text
-
-mark {
-  @extend %highlight-mark;
-}
-
-// Superscript / Subscript
-
-sub,
-sup {
-  // Prevent `sub` and `sup` elements from affecting the line height in
-  // all browsers.
-  font-size: var(--fs-xs);
-  line-height: 0;
-  position: relative;
-  vertical-align: baseline;
-}
-
-sub {
-  bottom: -.25em;
-}
-
-sup {
-  top: -.5em;
-}

assets/sass/components/highlight-mark/_highlight-mark.scss

@@ -1,11 +0,0 @@
-// Highlight mark
-//
-// The "new" or "updated" marker. This is a very thin component. A front-end
-// developer may choose to delete this component and just style the `<mark>`
-// element directly.
-
-.highlight-mark,
-%highlight-mark {
-  color: var(--color-mark-highlight);
-  background-color: var(--color-mark-bg);
-}

assets/sass/mixins/image-url/_image-url.scss

@@ -1,50 +0,0 @@
-// stylelint-disable function-url-quotes
-
-// The relative path from the css directory to the sass directory.
-$image-url-path-to-source: '../sass' !default;
-// The relative path from the root sass directory to where your components usually lie.
-$image-url-subdirectory: 'components' !default;
-
-// image-url()
-//
-// If you include your images next to your component Sass files, you need to
-// specify a url() to point from the generated CSS to the Sass source like this:
-//
-// ```css
-// content: url(../sass/components/is-quite/long.svg);
-// ```
-//
-// With the `image-url()` function the path to all your components is assumed to
-// start with `../sass/components/` and you just need to give it the last, short
-// bit of the path in your Sass code like this:
-//
-// ```scss
-// content: image-url(is-quite/short.svg);
-// ```
-//
-// If you want to point at an image that is not in the components sub-directory
-// of your sass directory, you can override the default $subdirectory by
-// passing it in as the first parameter of `image-url()` like this:
-//
-// ```scss
-// content: image-url(base, grouping/blockquote.svg);
-// ```
-//
-// which would output `url(../sass/base/grouping/blockquote.svg)`.
-//
-// $subdirectory   = $image-url-subdirectory - Optional. The relative path from
-//                   the root of your Sass source to the sub-directory where
-//                   components usually lie.
-// $path           - Required. The path to the image relative to the
-//                   `$subdirectory`.
-// $path-to-source = $image-url-path-to-source - Optional. The relative path
-//                   from the css build directory to the sass source directory.
-@function image-url($subdirectory, $path: null, $path-to-source: $image-url-path-to-source) {
-  // If only 1 parameter is given, its value is intended for the $path.
-  @if type-of($path) == 'null' {
-    $path: $subdirectory;
-    $subdirectory: $image-url-subdirectory;
-  }
-
-  @return url(unquote($path-to-source + '/' + $subdirectory + '/' + $path));
-}

assets/sass/styles.scss

@@ -46,7 +46,6 @@
 @import 'components/grid-stack/grid-stack';
 @import 'components/header/header';
 @import 'components/hidden/hidden';
-@import 'components/highlight-mark/highlight-mark';
 @import 'components/icon-inline/icon-inline';
 @import 'components/language-selector/language-selector';
 @import 'components/list-straight-left/list-straight-left';