add picom-conf (GUI) as link / option [suggested feature] [low Prio]

[2387skju]

Add link to GUI Picom-conf as option in window-manager drop-down.

Currently I'm not sure any more, if this feature really a good Idea. Therefore I've a added a few info, about how to recover / reset the window-manager.

This is Picom-conf ( Screenshot ):

Screenshot:

As text:

☑ I know how to restore my Desktop - [ 🛟 Info ]
Buttons: Reset to default preset - [ Open Picom-Conf ] - [ Restart Picom ] - Text-link: Open Config file

Info Screenshot:

Info as text:

Here you can can open GUI Tool Picom-conf or edit the config manual.
⚠ Warning: Both could be a little bit risky. Your Desktop can easy damaged permanent (e.g. all windows are nearly permanent invisible).
So, it is important for you to know, how to restore your Desktop. Please write this down (on paper) note:
Restore with this commands / keys:
CTRL + ALT + F1
...do login as user...
pkill picom
rm .config/picom.conf
CTRL + ALT + F7
Only if you understand (and tested) these command you should continue

So mainly, this adds only a link to GUI Picom-Conf.

This is TODO: How to handle the autostart.
Deleting OR bedder disable of autostart of Picom is required ( see #108 ). Delete is currently included here.
I suggest to wait for merge of Pull-Request "rework: autostart managment: disable autostart by overwrite with a local file, instead of delete the system-wide", then replace Dialog with self.disable_autostart('picom.desktop', 'Reason: parallel running will not disable composite.').