Create a GitHub PR for incoming comments

[penguineer]

Uses the following API endpoints for create a GitHub PR with the provided comment:

• https://docs.github.com/en/rest/pulls/pulls#create-a-pull-request
• https://docs.github.com/en/rest/repos/contents#create-a-file
• https://docs.github.com/en/rest/git/refs

There are available libraries for accessing the GitHub API.
However, there is not a lot of documentation. It turned out to be easier to call the API directly.