Serge

Add `SetCallbacks` function to packbuilder which invokes `git_packbuilder_set_callbacks` and allows packbuilder progress information to be reported back to the caller. https://libgit2.org/libgit2/#HEAD/group/packbuilder/git_packbuilder_set_callbacks

### TL;DR Migrate from Travis CI to GitHub Actions and update dependencies. ### What changed? - Replace Travis CI with GitHub Actions for CI/CD - Add a new CI workflow...