fix: minor improvements for osx compat

[andreaTP]

Tweaks and improvements of the template after #68

I believe that this should also fix asdf-vm/actions#548

[jthegedus]

Thanks for taking the time to PR this, but I don't believe it is the right solution to this problem.

It seems the template had an issue with the latest-stable sed command which was fixed in #65. This sed issue was causing the macos runner test failures because it couldn't resolve the version properly from that script.

The changes proposed here change much more than what would have been required to resolve that issue. The change from .tar.gz. to .zip for instance. This template is just a starting point for plugin authors, changes to the file type, decompression etc are expected to be done on a case by case basis, this plugin template cannot cover it all.

If you find more universal solutions, please raise issues to discuss or further PRs, contributions and discussions are welcome!

[andreaTP]

Make sense to me, thanks for getting back! 👍