[css-font-loading] Add issue about the base url used to resolve relative urls in FontFace constructor.
[css-font-loading] Sigh, make FontFaceSet extend EventTarget rather than implements it.
[css-font-loading] Expose CSSFontFontFaceLoadEvent to workers properly.
[css-font-loading] Rename the LoadEvent stuff to use FontFaceSet rather than CSSFontFace in the name.
[css-font-loading] Switch from 'await a stable state' to just use 'queue a task'.