Yes! You can use the pgxn-tools Docker image as part of your release workflows. It supports both testing an extension with multiple versions of Postgres, as well as releasing extensions on GitHub and PGXN. For details, check out these blog posts:
There is! Install it with this command:
sudo easy_install pgxnclient
If you use Homebrew:
brew install pgxnclient
Then you can install PGXN extensions with a simple command:
pgxn install pair
Run pgxn help
to get a list of supported commands; or check out the
introductory blog posts, the complete documentation or the source
code.