Rename master to main

[tdegeus]

Has the time come that we should make the change master -> main? It's starting to become one a few projects I participate on that is still on master

[spectre-ns]

@tdegeus I'm curious what the advantage is. I might do this for my repos if there is a trend toward doing this.

[tdegeus]

No practical advantage, GitHub's reason is political.

Besides, I find it simply annoying that some repos use master and some main. Now that the majority seems to be main (at least that is my impression) it might be nice to just adhere to the majority.