Browser-compat-data: Mark obsolete HTML features as deprecated

[foolip]

Everything in https://html.spec.whatwg.org/multipage/obsolete.html is standardized with no intention of ever being removed from the web platform, but obsolete and discouraged from use. https://github.com/mdn/browser-compat-data/pull/7252 marked document.all as deprecated on these grounds, and we should do it for the rest of these features.

@sideshowbarker this may interest you.

[sideshowbarker]

Progress report: For all features in the first two subsections of https://html.spec.whatwg.org/multipage/obsolete.html — which is basically about obsolete elements and attributes I’ve already raised PRs (all of which have now already been merged).

What remains is to raise PRs for the final subsection at https://html.spec.whatwg.org/multipage/obsolete.html#requirements-for-implementations — which is about obsolete APIs and obsolete members of APIs. I’ll spend some time looking at that now.

[Elchi3]

This is really great, @sideshowbarker! :tada:

[foolip]

I realized after merging https://github.com/mdn/browser-compat-data/pull/7589 that a few attributes weren't correctly marked as deprecated. Mentioning here so that it won't be overlooked before closing this issue. @vinyldarkscratch can you update those statuses?

[sideshowbarker]

What remains is to raise PRs for the final subsection at https://html.spec.whatwg.org/multipage/obsolete.html#requirements-for-implementations — which is about obsolete APIs and obsolete members of APIs. I’ll spend some time looking at that now.

Update: I got through a good part of that section before I needed to be away for a bit. But I’ll be getting back to it again soon.

I realized after merging #7589 that a few attributes weren't correctly marked as deprecated. Mentioning here so that it won't be overlooked before closing this issue. @vinyldarkscratch can you update those statuses?

I guess that means I didn’t reach yet reach HTMLHRElement in my journey through the rest of that HTML spec section. Anyway, I’ll make sure it doesn’t fall between the cracks — either by raising the PR for it myself once I reach that point in my audit of BCD against the spec, or else by reviewing @vinyldarkscratch’s PR, if she happens to get to it before I manage to.