errors in test.yaml

[dornech]

I think there are two errors in test.yaml.

1. mixing python_version and python-version
   
   This leads to following error in execution:
   

2. I think test exectution command should read hatch test (what should be equivalent to pytest tests) and not hatch run test:pytest
   The current setting creates Github Action jobs according the matrix and then refers to the hatch test environment containing a matrix as well. This results in job like this:
   

[dornech]

Improvement in #21