Uses environment variables instead of hard coding the "deck" user/group.
This adds support for systems other than the steam deck that are using the DeckUI.

* Use Environment Variables

* Use method to get USER from a systemd root process

* Fix imports. Add get_user and get_user_group methods in helpers.py. Removed duplicated code

* Add separate setters/getters for user vars. Ensure sleep prevents race condition of user setter in while loop

* Create uninstall.sh

* Update uninstall.sh

First pass for a version that looks similar to the install scripts

* Update readme with uninstall info

Add uninstall script info to readme

* Update dist/uninstall.sh

Only remove services for now

Co-authored-by: TrainDoctor <11465594+TrainDoctor@users.noreply.github.com>

* Adjust echo to accurately reflect script actions

No longer deletes installed plugins, adjusted echo to match actions.

Co-authored-by: TrainDoctor <11465594+TrainDoctor@users.noreply.github.com>