Add instructions for making a new maint branch to EndOfLifeTor.md, and rename the file
When we stop supporting a tor release, we follow the instructions in EndOfLifeTor.md. But we don't have any instructions for a new maint branch or new release series.
Since the instructions are pretty similar, we should put them in EndOfLifeTor.md, and then find a better name for that file.
Nick will write up a pad, and then I will put it in the file.
Gaba, I think this could be a Sponsor 31 task, because it is about best practices.