idea: self update should show/offer to show the changelog from the version

[xaf]

This could be done by adding into https://github.com/XaF/homebrew-omni/blob/main/Formula/resources/omni.json a changelog field with the list of things that changed.

Maybe moving to Conventional Commits would also allow for easier/cleaner changelog generation, since if we want to show the changelog, we probably want to hide most of the chores.

[xaf]

Moved to conventional commits, so changelog can be auto-generated for releases. Still hesitant if this should be done, or just a link to the release notes provided. Aligning for the latter at the moment, or for not changing anything!