Set up release workflow

[fingolfin]

For making a release from the GitHub web interface. Usage instructions at https://github.com/gap-actions/release-pkg/.

[wilfwilson]

The CI will fail here until #24 is merged.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.48%. Comparing base (24ceb5d) to head (db48853).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master      #25       +/-   ##
===========================================
+ Coverage        0   55.48%   +55.48%     
===========================================
  Files           0       25       +25     
  Lines           0     1386     +1386     
===========================================
+ Hits            0      769      +769     
- Misses          0      617      +617     

see 25 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[wilfwilson]

The CI now passes and this looks good to me.

[dimpase]

Thanks!