Make Keywords section in desktop translatable

[cibersheep]

Dash in Lomiri uses keywords to find apps. So it's a great feature you already support. They need to be localized though

https://github.com/costales/unav/blob/master/app.desktop#L4

Example: https://gitlab.com/cibersheep/tfamanager/-/blob/master/CMakeLists.txt#L59

Let's see if I can find some time to add this