[FEATURE] Add Changelog feature for addon devs to display what is new in an addon update

[luzpaz]

Is your feature request related to a problem? Please describe. Not necessarily. It would be nice as an end user to know what was updated in the latest addon that needs to be updated.

Describe the solution you'd like Perhaps a dialog box or some sort of output when installing an update of a specific addon to output what has changed in this version update.

Describe alternatives you've considered Providing a link back to the repository somehow?

Additional context Several addon devs provide changelogs in their READMEs. For example:

• https://github.com/mwganson/Editor_Assistant#changelog
• https://github.com/Zolko-123/FreeCAD_Assembly4#release-notes
• https://github.com/shaise/FreeCAD_SheetMetal#release-notes
• https://github.com/shaise/FreeCAD_FastenersWB#release-notes-berberic2