This commit adds:
+ a few tags to `scribble/html` (by extending the list in `scribble/html/html`)
+ even more tags to `scribble/html/extra`,
these tags are "likely" to cause namespace issues (time, map)
or are uncommon / esoteric (rb, ruby, svg)
+ a test in `scribble/html.rkt` that the tags from
- `scribble/html/html`
- and `scribble/html/extra`
match a master list from the whatwg specification*
* https://html.spec.whatwg.org/multipage/#toc-semantics
