Add documentation of new dialog light dismiss behaviors

[mfreed7]

MDN URL

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dialog

What specific section or headline is this issue about?

No response

What information was incorrect, unhelpful, or incomplete?

There are new dialog behaviors, proposed here:

whatwg/html#10737

Specifically, a closedby attribute can be used to enable "light dismiss" behaviors for <dialog>, akin to popovers. Also, a new dialog.requestClose() method allows a programmatic request to close the dialog, which goes through the cancel/close process.

What did you expect to see?

Documentation

Do you have any supporting links, references, or citations?

whatwg/html#10737

Do you have anything more you want to share?

I'm hoping to ship this in Chrome M134, pending approvals, etc.

[hamishwillee]

@mfreed7 Thanks for this. MDN doesn't document things until there is an implementation, and from those linked bugs there isn't one yet right?

FWIW I'd like to do this - spent some time on popovers/dialogs recently so its in my head.

[mfreed7]

@mfreed7 Thanks for this. MDN doesn't document things until there is an implementation, and from those linked bugs there isn't one yet right?

Not yet. This is somewhat chicken-and-egg, since the WHATWG process requires that an MDN issue be filed before the new spec can land (see the second-to-last checkbox on whatwg/html#10737). And at least Chromium's shipping process generally wants a landed spec before shipping. So MDN has to come first.

FWIW I'd like to do this - spent some time on popovers/dialogs recently so its in my head.

Awesome, thanks!