Add `<Html>` meta component

Editor assessment

The subject names the new component exactly — the `<Html>` meta component — so the header communicates the feature without the diff, and feat classifies it correctly with scope omission tolerable since the subject carries the target. Hygiene is clean: the capitalization is a permitted stylistic choice, length is sensible, and no trailing period or ticket junk appears. The two Co-authored-by trailers are well formed. No body is present, tolerable for a small component addition, though a line on what it renders would add value. A good, publishable example.