[ci] Use a token to upload codecov reports

[vgvassilev]

Fixes #68

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.60%. Comparing base (bb9bb85) to head (27fca7e).
Report is 10 commits behind head on main.

❗ Current head 27fca7e differs from pull request most recent head 5807e07. Consider uploading reports for the commit 5807e07 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #70      +/-   ##
==========================================
+ Coverage   49.14%   51.60%   +2.45%     
==========================================
  Files          15       15              
  Lines         643      593      -50     
==========================================
- Hits          316      306      -10     
+ Misses        327      287      -40     

see 12 files with indirect coverage changes

see 12 files with indirect coverage changes