proposal(pr): use github api directly rather than CLI for github operations

[coillteoir]

Problem

Using the github CLI for pull requests and other github related things requires an extra package install.

Proposed solution

• Use the github API directly via a client library.
• Authenticate using access token in gitconfig, env variable, or other config format.

Possible future work

Removing the CLI as a dependency, also opens up the ability to build up compatibility with other Git providers, such as GitLab, or Gitea via a shared interface.