feat: add codecov

[LesnyRumcajs]

Summary of changes

Changes introduced in this pull request:

• add code coverage to the repository

Reference issue to close (if applicable)

Closes

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),

[hanabi1224]

@LesnyRumcajs Hmm we get codecov uploading error even with the ENV VAR

[LesnyRumcajs]

@LesnyRumcajs Hmm we get codecov uploading error even with the ENV VAR

It was an intermittent failure.