* Fix GitHub Actions
* Disable tests with `musl` for arm64 because there's no `libv8-node` gem for aarch64-linux-musl at the moment
* Fix tests on older Ruby versions by running `gem update --system`
* Removes macOS 10.15 (it will be unsupported by 2022-08-30 anyway)
* Adds macOS 12 to the matrix
* Run TruffleRuby job on macOS as well
* Use `ruby/setup-ruby` action where possible and update `actions/checkout` to v3
* Run tests for pull requests
* Raise sleep duration in tests to fix CI failures on macOS
* Add tests for mutable string arguments and return values
Gerhard Schlager