Change Branch Master to Main

[Akash Rajvanshi]

As per the new repositories in GitHub - The default branch is the main

# .github/workflows/main.yml
branches:
      - master

so as a new user commits the code, it will go to the main branch instead of master and which will not trigger an action.

# .github/workflows/main.yml
branches:
      - main

[Erik Newhard]

Duplicate of #56