Add support for directives on directive definitions

[BoD]

Allow directives on directive definitions, based on this spec PR which introduces this syntax:

directive @onDirective on DIRECTIVE_DEFINITION

directive @foo @onDirective on OBJECT

directive @baz @deprecated(reason: "...") on OBJECT

extend directive @quux @deprecated(reason: "...")

Disclaimer

First time on this codebase and am also not a JS/TS person, so obvious mistakes and/or missing pieces are very likely 😅 Any help and feedback to improve this PR are very welcome 🙏. The tests seem to pass but additional tests may be needed.

[vercel]

@BoD is attempting to deploy a commit to the The GraphQL Foundation Team on Vercel.

A member of the Team first needs to authorize it.

[leebyron]

Update includeDeprecated arg per @benjie 's comments, then we'll merge

[BoD]

Just made the change for includeDeprecated: Boolean! + added one test.

[jerelmiller]

Had a few suggestions, mostly around types, but otherwise looks good from my end!

You probably want to get a proper review from someone who knows the conventions in this codebase better than I do, but wanted to try and help move this along in some way!

[benjie]

I've not fully reviewed this PR, but the changes since Lee's review all look fine to me - thanks @BoD! 👍