Input (continued)

[autonome]

Migrating the work from #1441

The Caniuse entries seem to line up, so @petele already did that 🎉

I fixed the descriptions to be clearer when they contain a list of type values. I don't like the inconsistency w/ the single-type version, but is probably ok like this.

The idea of variants of a specific attribute value for a specific element being standalone features seems fine, but I don't know if that fits into how we've been thinking about the html-elements group. Do we expect that group to be each element, once? Or is this fine?

Fixes #1441

[ddbeck]

Several suggestions here, mostly about descriptions. The big things are:

• Let's treat almost all input types as if they were distinct elements (though a few can be grouped together). See line comments for details about this.
• Lots of non-reals have been fixed. Uncommenting them and refreshing will probably fix nearly all of those comments.
• Changing a feature's ID is a breaking change. Let's set that aside for a minute.

[autonome]

ok ready for another review pass. not stoked on the "represents" language from the original PR, so lmk if you think needs reworking.

[ddbeck]

This is pretty great. I'm going to land this now, then revise all the input descriptions together (including ones not part of this PR) at once. Thank you, Dietrich!