add command to reset a users dconf settings

admin-guide/configuration/desktop/program_starter.md

@@ -15,6 +15,13 @@ Note that this will only set the default configuration which can be changed by t
 
 To reset the user specific configuration run
 ```
+# only reset gnome dconf settings
+dconf reset -f /org/gnome
+
+# reset all dconf settings
+dconf reset -f /
+
+# if the commands above does not work
 rm  ~/.config/dconf/user
 ```