envmanager: Add overlay configs through XDG_CONFIG_DIRS

Devin Linrequested to merge
work/devinlin/envmanagerkwinoverlay into master

We currently directly write our settings to ~/.config/kwinrc and ~/.config/ksmserver.

Instead, create a separate config file with our settings (in ~/.config/plasma-mobile), and in startplasmamobile, add that path to XDG_CONFIG_DIRS. These options will be applied in the mobile session, unless the user explicitly sets the config option.

Edited by Devin Lin

Merge request reports