Change default branch name

[pchickey]

The WASI subgroup is changing the default branch names in all repositories to main.

Please consider this a tracking issue. It is not intended for public debate.

• Change branch name
• Update CI
• Update build scripts
• Update documentation

[sunfishcode]

Github how as an update here. They will be "investing in tools to make renaming the default branch of an existing repository a seamless experience for both maintainers and contributors", so it sounds like we should wait for now and see what they come up with.

[pchickey]

The default branch has been renamed!
master is now named main

If you have a local clone, you can update it by running:

git branch -m master main
git fetch origin
git branch -u origin/main main

[pchickey]

AFAICT, no CI, build scripts, or documentation changes were required in this repo.