appdata: add <releases>

This is the last stable release. (<releases> is now mandatory on
Flathub.)

This should be updated for each new release, ideally with a
<description> containing release notes.
4 jobs for appdata-releases in 11 minutes and 15 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Test
passed #391638
flatpak

00:04:09

 
  Cross Environment
passed #391639
fedora:latest

00:06:39

 
  Deploy
passed #391640
review

00:00:26

manual #391641
allowed to fail manual
stop_review