Audio link button

[trymeouteh]

To have an ql-audio class for buttons in the toolbar to insert audio from a URL.

It will insert an <iframe> of the media and when you use getSemanticHTML(), it will convert the ifrane into an <a> tag.

The same as the ql-video class button but with an audio icon.

And to create an event method to detect when an audio URL is being inserted
#4583