Changelog

Changelogs can be displayed on Flathub and within distro app updaters, all that's needed is an `.appdata`/[.metainfo.xml](https://docs.flatpak.org/en/latest/conventions.html#appdata-files) file.

See these examples of another app's [appdata.xml](https://github.com/flathub/io.github.trigg.discover_overlay/blob/master/io.github.trigg.discover_overlay.appdata.xml), and how their changelog is [displayed on Flathub](https://flathub.org/en-GB/apps/io.github.trigg.discover_overlay).

Start by reviewing the linked Flatpak conventions and the two example appdata.xml files. Identify where this repository's app metadata belongs, add the changelog metadata there, and verify that the resulting .appdata or .metainfo.xml file is accepted and displays the changelog on Flathub or in distro app updaters.

Written by the indexing model from the issue text.