Add missing dependencies "@babel/generator", "common-tags"

[elliottsj]

Fixes #1070

TODO:

• Update CHANGELOG.md* with your change (include reference to issue & this PR)
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass

*Make sure changelog entries note which project(s) has been affected. See older entries for examples on what this looks like.

[trevor-scheer]

@elliottsj it looks like this issue exists in the other codegen packages as well (I see scala, TS, and swift importing from common-tags). Would you mind adding to those as well?

Also see @babel/generator is imported in the TS generator package.

Thanks for taking care of these!

[elliottsj]

Done!

[trevor-scheer]

Thanks so much!