Rename primary branch to main

[t3rryM]

Please rename your primary branch to Main to conform to JPMC inclusivity standards.
If you need assistance, contact JPMC GitHub Admins (internal).

[nazq]

@t3rryM , Doesn't look like I have permissions to set main as the default. If you can do that then I'll drop master

[t3rryM]

Hi, let's connect internally about this change.