Rename primary branch to main

[mhdawson]

We are going through all of the node.js repositories to rename the primary branch to main. Please see nodejs/node#33864 for more context.

I also don't see any references to master other than URL links which the auto redirect should handle so I don't think there should be issues with the rename.

Please let me know if there are any concerns otherwise I'll look to do the rename Friday May 4th.

[mhdawson]

@indutny any concern over the rename?

[indutny]

No concern, but CI. Thanks!

[mhdawson]

Thanks, renamed.