Update RELEASING with revisioning instructions

[Lucsanszky]

Description

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated
• When applicable, versions are updated in .cabal and CHANGELOG.md files according to the
  versioning process.
• The version bounds in .cabal files for all affected packages are updated. If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
• All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages. New section is never added with the code changes. (See RELEASING.md)
• Code is formatted with fourmolu (use scripts/fourmolize.sh)
• Cabal files are formatted (use scripts/cabal-format.sh)
• hie.yaml has been updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[Lucsanszky]

I will also add a section with general instructions to sum things up after the more specific step-by-step instructions and perhaps add the actual git commands in the general setup section but this is roughly it. Hopefully it is clear and detailed enough.

[teodanciu]

These are great details, thank you for writing them down so thoroughly!
I just had a suggestion about switching the sections: starting with the overview of what the process is and when we need to do it, and then following with the example (maybe also, if possible, naming the specifics of the example, eg: creating a revision for this package at that commit), just so it's easier to understand for someone who is not familiar with revisions (like me 😬 )

[teodanciu]

Looks good to me, awesome!