Change `master` branch to `main`

[djwf]

There are numerous articles out there that talk about why, here's one: https://www.jumpingrivers.com/blog/git-moving-master-to-main/

[epage]

So far I've not been updating all of my existing repos but all new repos are using main (its a bit of work to update 20+ repos for low touch crates)

[djwf]

I'll have to think on it, but I'd like to move it over, and would be willing to do the lion's share of the work to do so. It's not urgent, though.

[epage]

The switching cost is not just the work to do it in github but every developer's local forks. The overall cost is why I've been hesistant.