Support other repos and base branches

[kfcampbell]

This is the same PR as #563 but proposed from within the repository rather than a fork outside it for testing purposes.

It adds:

• A way to make changes in a repository other than the repository the Action is running on.
• The capability to update a base branch other than the default branch.

[gr2m]

Looks like CI on master fails as well, and no idea why, I didn't change anything for a while 🤷🏼
#601

Looks like something changed with actions instead, this won't be easy to figure out I fear

[kfcampbell]

I've solved a failing issue I was seeing earlier due to the owner variable being undefined in the checkOutRemoteBranch function. When this is ready to be merged/released, I'll remove the dist/index.js file from the git tree. Until then, it's required to be able to use the PR as-is.

[kfcampbell]

For an example of this running successfully, see this Actions run that generated this PR.