Improve desktop entry (#604)

* Added category `FileTools`
See https://specifications.freedesktop.org/menu-spec/latest/apas02.html

* Added `Keywords`
See https://specifications.freedesktop.org/desktop-entry-spec/latest/ar01s06.html

* Added `zh_CN` & `zh_TW` comments

data/com.github.qarmin.czkawka.desktop

@@ -6,7 +6,10 @@ Name=Czkawka
 Name[it]=Singhiozzo
 Comment=Multi functional app to clean OS which allow to find duplicates, empty folders, similar files etc.
 Comment[it]=Programma multifunzionale per pulire il sistema, che permette di trovare file duplicati, cartelle vuote, file simili, ecc...
+Comment[zh_CN]=可用于清理文件副本、空文件夹、相似文件等的系统清理工具
+Comment[zh_TW]=可用於清理重複檔案、空資料夾、相似檔案等的系統清理工具
 Icon=com.github.qarmin.czkawka
-Categories=System;
+Categories=System;FileTools
+Keywords=Hiccup;duplicate;same;similar;cleaner
 StartupWMClass=czkawka_gui
 TryExec=czkawka_gui