added trailing separator on categories

Слиты xottab-duty запросил слияние github/fork/KaMeHb-UA/patch-1 в xd_dev

Created by: KaMeHb-UA

most DEs deal with it right but some envs requires standard appearance (for example, appimagetool) https://standards.freedesktop.org/desktop-entry-spec/1.0/ar01s03.html