export const, function and class binding

[jasonlyu123]

#647
We might have to try finding a way to typecheck it later. Currently can't tell if that's a binding or normal props.

[dummdidumm]

Do you remember why we originally did not mark these as possible props? EDIT: Ok I guess precisely because they are not valid input props, and only valid binding props?

[jasonlyu123]

Yeah, I guess it's because of the warning if you use it as a input props. Doesn't know it can be binded, didn't see it on the docs.

[dummdidumm]

This and the if-scoping feels to me like the "convert to JSX"-approach has some limitations we increasingly have to hack around against. Not sure if we have good alternatives though.