Moving sass and js files in to the assets directory.

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

@@ -0,0 +1,12 @@
+// 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: $mark-highlight;
+  // Remove background highlighting from <mark> in normalize.
+  background-color: transparent;
+}