Added an appdata.xml file for Linux software galleries
Addresses https://github.com/themanaworld/tmwa-client-data/issues/104 for all distributions. See https://en.opensuse.org/openSUSE:AppStore for more information.
Addresses https://github.com/themanaworld/tmwa-client-data/issues/104 for all distributions. See https://en.opensuse.org/openSUSE:AppStore for more information.