Auto update metainfo on release

[ColinKinloch]

Your suggestion

Currently 2.1 isn't in the releases section of https://github.com/cemu-project/Cemu/blob/main/dist/linux/info.cemu.Cemu.metainfo.xml

Since I created it the flatpak has had a script to add the field for each experimental release. This script will likely break if the releases field is kept up to date here.

An easy option is to use the https://github.com/flathub-infra/flatpak-external-data-checker which will update a metainfo hosted on the flathub repo. I don't love that option as that metainfo would need to be kept up to date with the one on this repo, and it wont add a link to the change log.

It would be cool if there was a non manual way to keep it up to date here.