yelp appdata file

[Kalev Lember <kalevlember gmail com>]

Hi,

I went ahead and pushed an appdata file for yelp to git and didn't
branch yelp for 3.28 before that. I hope it's ok, as it's basically
fixing untranslated strings in gnome-software (almost all downstreams
were already shipping untranslated appdata files as downstream patches).

piotrdrag +1'd the plan on IRC and Daniel Mustieles said in 2014 that
this has +1 from the i18n team :)

https://bugzilla.gnome.org/show_bug.cgi?id=722763

Thanks,
Kalev