IDL for HTMLScriptElement needs to escape "async"

[domenic]

It is now a Web IDL keyword. #4833 tracked how this broke our build, but that got fixed. Now we just need to update our IDL to be valid.

[annevk]

See whatwg/webidl#769 so maybe @tabatkins should update their IDL parser?

[domenic]

Yeah, or rather, we should land the heycam/webidl change -> plinss/widlparser change -> tabatkins/highlighter change -> whatwg/html-build change -> rebuild the HTML Standard on Travis. Dependency fun times :)

[tabatkins]

At least it's fast once the update lands in widlparser. ^_^

[domenic]

Fixed in IDL!