Automatically tag releases in dotnet-security-partners/dotnet repo

We send releases to partners as tags as part of source-build servicing hand-off each month. The tagging process should be automated.

I have written a script which I use to do this on my local machine: https://gist.github.com/lbussell/2e3f445668e8c1f1f8eb83a8fd1ff4ad