Support WebAudio APIs

[alecgorge]

Is your feature request related to a problem? Please describe.

I would like to use Ultralight for a webapp that plays music. We make use of the HTML5 audio tag and the WebAudio classes themselves. I'd say HTML5 audio tag is higher priority but it'd be nice to have both.

Describe the solution you'd like

1. https://html.spec.whatwg.org/multipage/media.html#the-audio-element
2. The WebAudio API as a whole is huge so I don't view this as a priority: https://www.w3.org/TR/webaudio/

Describe alternatives you've considered

None? There's no way to play audio.

Additional context
Add any other context or screenshots about the feature request here.

[raff]

Is this a matter of enabling WEB_AUDIO in WebCore and then tweak something in here ? Or there is more ?

[adamjs]

Duplicate of #217 (in progress).