Document /automate release notes flow

[MattDodsonEnglish]

At minimum, we need a process in RELEASES.MD that documents requirements and relevant Hugo code. In an ideal world, all file movement is automated:

Release notes flow:

1. Gather PR with release notes, versionCompat, checksums
2. Merge PR with into last
3. On tag:
   1. Copy latest from HEAD-1 to /versions/
   2. Add cascade.v: to /versions//_index.md | perhaps unnecessary if versions template is re-written to use file path