Versioning instructions

Manual, clunky but it works

1. Copy preen.rb
2. Rename old preen.rb to preen@X.X.X.rb
3. Visit the Github Release page for the version you want to expose via Homebrew (e.g. this is the page for v0.2.4)
4. From here, grab the arm64 checksum and paste it into the sha256 field in the file now named preen.rb
5. From the GH Release page, copy the arm64 tar ball link and paste it into the preen.rb URL field
6. yer done