narrow popover related attribute types to just `<button>` and `<input>` elements

[thescientist13]

Current State

Coming out of #229 , had to manually extend our types to support popovertarget and popovertargetaction explicitly. However, per the spec it should really only apply to <button> and <input> elements.

Desired State

This should work

<button popovertarget="mobile-menu" popovertargetaction="hide">
  Close
</button>

But this should error

<span popovertarget="mobile-menu">Close</span>

Additional Context

Curious in general though why it doesn't work? Shouldn't TypeScript's DOM lib support this already? 🤔
https://github.com/microsoft/TypeScript-DOM-lib-generator

[LouisLau-art]

Opened a PR to narrow popovertarget/popovertargetaction to /: #237

[thescientist13]

Oh great, thank you for that @LouisLau-art !

Let me check that out in the next day or so (just in the process of launching the new site for WCC 😃 )