Update handling of action outputs

[blink1073]

cf https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#environment-files

h/t @gabalafou

[codecov-commenter]

Codecov Report

Base: 81.26% // Head: 81.16% // Decreases project coverage by -0.09% ⚠️

Coverage data is based on head (b116263) compared to base (86f2b4d).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #442      +/-   ##
==========================================
- Coverage   81.26%   81.16%   -0.10%     
==========================================
  Files          20       20              
  Lines        2823     2824       +1     
  Branches      364      365       +1     
==========================================
- Hits         2294     2292       -2     
- Misses        397      399       +2     
- Partials      132      133       +1     

Impacted Files	Coverage Δ
jupyter_releaser/util.py	69.71% <0.00%> (-0.55%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.