Add HTML5 tags and attributes

[beargiles]

Discussed in #2226

^{Originally posted by beargiles November 15, 2024}
Add HTML5 tags and attributes.

HTML5 adds many elements that provide semantic context for parsers - e.g.,

, ,

etc at the structural level, or , , etc. at the text level. It also adds media controls (,

[jhy]

Dupe of #853, planned in #2284