Add an example on how to bump up versions in the changelog

[lehins]

Also chaneg the policy on where to add new entries in the changelog

Description

Slight improvement to RELEASING doc

Important change is the policy to add new entries in the changelog to the top. This turns out to be quite useful when a package is being released from behind master's HEAD.

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 (See RELEASING.md)
• Any changes are noted in 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

[aniketd]

Awesome! Thank you 🙌