Change default branch to main

[juliusgb]

If you forked this repo, then please do the following:

On your fork in GitHub, avigate to your fork in GitHub's UI -> Branches -> edit the default branch -> change its name to main

If you cloned your fork, then run the following in your git bash console:

git branch -m master main
git fetch origin
git branch -u origin/main main
git remote set-head origin -a