Changed files for default branch name switch to main from master

[eytanadler]

Purpose

Updated github action files and readme with name change of the default branch from master to main. The codecov badge link may need to change once it has been run.

Expected time until merged

Type of change

• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (non-backwards-compatible fix or feature)
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no API changes)
• [ ] Documentation update
• [x] Maintenance update
• [ ] Other (please describe)

Testing

Checklist

• [ ] I have run flake8 and black to make sure the code adheres to PEP-8 and is consistently formatted
• [ ] I have run unit and regression tests which pass locally with my changes
• [ ] I have added new tests that prove my fix is effective or that my feature works
• [ ] I have added necessary documentation

[codecov[bot]]

Codecov Report

Merging #382 (6b972ff) into main (95d0a0f) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #382   +/-   ##
=======================================
  Coverage   96.61%   96.61%           
=======================================
  Files          93       93           
  Lines        5912     5912           
=======================================
  Hits         5712     5712           
  Misses        200      200           

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