Separate github tokens for issue and project access

[aborgna-q]

As stated in the fine-access token documentation:

Each token can only access resources owned by a single user or organization.

This is a problem when using add-to-project with an issue and a project under different organisations, as both are accessed with the same github-token.
Currently the only way around this is to go back to using classic unrestricted tokens, without any kind of permissions control.

A simple solution to this could be to add an optional project-github-token that defaults to github-token. It can be ignored for most usecases, but it would let us keep using fine-grained tokens when targeting different organisations.

[Aceteimiaace316]

Good

[Aceteimiaace316]

Hey