Changing default branch name to 'main'

[kevinodotnet]

(Thanks for making python_koans. I just started running through it to brush up on Python in general (keeping skills sharper) and as I'm day-to-day working in Ruby, this makes it very natural!)

I was hoping you would consider changing the default branch in python_koans to main, the new default?

The process is pretty quick: https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/managing-branches-in-your-repository/changing-the-default-branch#changing-the-default-branch

Thanks!