Signing commit when creating PRs

[wusyong]

Currently, covector can't sign the commits, which makes merging PR impossible if there's a branch protection enforcing signing commits.
The only workaround is maintainer recommit with their signatures.
I would like to explore if covector can automate this.

[jbolda]

@wusyong, within the Tauri ecosystem, we are currently using the create-pull-request action to commit and open the PR. It has guidelines regarding enabling signed commits. We have looked at pulling some of this Github functionality into the action, but I anticipate that the exact same setup would be required.

https://github.com/peter-evans/create-pull-request/blob/main/docs/concepts-guidelines.md#gpg-commit-signature-verification