[C-1044] Allow public-only access to GitHub

[patrys]

What problem are you trying to solve?

I don't want crowd.dev to access our private repositories. Currently, I am forced to hand-pick repositories and I need to remember to edit the list if I create a new public repository.

What's your suggested solution?

Allow users to select between private and public access, granting crowd.dev access to all public repositories and only public repositories.

Examples (if relevant)

No response

Is anything blocking this from being implemented? (if relevant)

No response

Definition of Done

• [ ] Provide a way to automatically scope GitHub access to "all public repositories"

_{From SyncLinear.com | C-1044}