[js.html] wrong return type for MediaElement.play()

[mockey]

The play() function of the HTMLMediaElement
https://api.haxe.org/js/html/MediaElement.html#play
returns a Promise instead of Void as of late.
This is important for dealing with autoplay blocking in Chrome 66, e.g.

Once again my question: Is it possible to make a PR for changes in the (generated) JS-API?

[haxiomic]

Hey @mockey, it's fixed in the newer WebIDLs – when js.html is re-generated this issue should be resolved. In the meantime you can create a file js/html/MediaElement.hx in your project and fill it with the newer externs: https://gist.github.com/haxiomic/511e2e801fc82b791a0d44ef1f99b161

[haxiomic]

Resolved in #7354