Specify `autocapitalize`

[travisleithead]

Filing as an issue because this is implemented in WebKit, so has some degree of interop already.

This issue was transferred from the Bugzilla bug: https://www.w3.org/Bugs/Public/show_bug.cgi?id=12409 (which has links to other related bugs/conversations about this issue).

See Mounir's proposal here: https://github.com/mounirlamouri/html-autocapitalize/blob/master/proposal.md

We should figure this out for v.5.1.

[chaals]

This looks like it is still waiting for more implementation, although that seems likely to happen.

So the question is whether it should be HTML 5.1 or later. Leaving it without a milestone for now.

[travisleithead]

See also Issue #269

[chaals]

Where is this up to in implementation?

[cvrebert]

Implemented in Chrome: https://www.chromestatus.com/feature/4529989986811904