Appdata: Add copyright information

See https://blogs.gnome.org/hughsie/2013/10/01/copyright-in-appdata-files/ for details.
3 jobs for appdata in 3 minutes and 9 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #14530
run-appdata

00:00:05

passed #14529
run-tests

00:02:52

 
  Build
passed #14531
run-build

00:00:11