Show upgrade changelog

[BSick7]

Overview

When a module is pegged for an upgrade, it would be valuable to show a user what has been changed between the current infra and the new module version.

Details

When a user or automation publishes a new module, scan the CHANGELOG.md and store it in the module version. Then, when a user is prompted with a module upgrade, they should be able to see the CHANGELOG.md but only showing the text in that markdown document that's relevant to versions between the old and new version.