Add missing support for most critical APIs (like WebAudio and RequestAnimationFrame)

[cyrbon]

It seems that webkit supports webaudio api, but Haskell's bindings do not. I've seen several people using only GHCJS when using GHCJS-DOM only due to the lack of WebAudio or RequestAnimationFrame support. WebAudio is not only useful for audio but its API can be used for many types of signal processing and visualization which go beyond audio processing. So, support for WebAudio would open a whole new universe of possible applications, when compiling natively using ghcjs-dom and reflex-dom.

[hamishmack]

Combination of latest ghcjs-dom (uses ghcjs-dom-jsaddle when compiled with ghc) and jsaddle-webkit2gtk might help with this. Please give it a go if you have time.