Make various support updates to BaseAudioContext (#6051)
Make various support updates to BaseAudioContext (#6051)

Testing and code inspection confirm that Safari doesn’t support the
audioWorklet and createIIRFilter members of (Base)AudioContext, nor have
support for disabling normalisation.

Testing and code inspection also confirm that createConstantSource, which
had been marked as supported in Safari, isn't actually supported in Safari.
mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data