Change starting branch's name from master to main

[HenriqueAJNB]

Can the starting branch be renamed from master to main to keep synced with this GitHub change?

If this is an easy task, I can handle it, but I never worked on this project; I just used it as a standard user and not a collaborator.

[jmegner]

As far as I can tell, this repo has been abandoned (and I can not reach the owners) and this request already has a few open issues and PRs. I have a fork at https://github.com/jmegner/visualizing-git that has merged in some of people's PRs, including ones that change the default/starting branch name to main, like #137.