Have PermissionDeniedError added to WebIDL

[foolip]

https://w3c.github.io/push-api/#exceptions

This should ideally be in http://heycam.github.io/webidl/#dfn-error-names-table so that other specifications can use it. Please file an issue at https://github.com/heycam/webidl/issues if you agree.

Note that NotAllowedError was added in whatwg/webidl#85 and this is very similar. It might not make sense to keep both, which would be resolved by trying to get both into the same spec :)

[mvano]

This is a duplicate of #107. I hope you don't mind if I close this one.

As to the idea: it would be real nice to get this formalized.

[foolip]

Thanks, will comment in Bugzilla.