Add <mark> element (web-platform-dx#1420)

Author: petele

features/draft/html-elements/mark.yml renamed to features/mark.yml

@@ -1,6 +1,5 @@
-draft_date: 2024-06-05
 name: <mark>
-description: The `<mark>` element TODO.
+description: The `<mark>` element represents text which is marked or highlighted for reference or notation purposes.
 spec: https://html.spec.whatwg.org/multipage/text-level-semantics.html#the-mark-element
 group: html
 compat_features: