Rename of master branch to main in github

[galak]

As part of our inclusive language efforts we are changing the development branch in git from master to main.

You will need to utilize at least west 0.10.1. If you have an existing checkout of zephyr you'll need to make the following changes:

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

[mbolivar-nordic]

You will need to utilize at least west 0.10.1.

To expand on this a bit: this is required for plain west init to work to initialize a workspace.

You can still specify west init --mr main with older versions of west after this change.

[galak]

You may also want to make this change in your fork of Zephyr on GitHub.

You can find details on how to do that here:

https://github.com/github/renaming

[nandojve]

Can I assume this will be last modification before next tag release?