feat: added compatibility with ChimeraOS configuration and device-quirks

Signed-off-by: Boris Yumankulov <boria138@altlinux.org>

README.md

@@ -1,13 +1,48 @@
 # PortProtonQt session
 
 This project is not affiliated with Valve (wide inspiration was taken from
-their work on the SteamDeck). This configuration depends on [gamescope-session](https://raw.githubusercontent.com/ChimeraOS/gamescope-session) from the ChimeraOS project. and [portprotonqt](https://git.linux-gaming.ru/Boria138/PortProtonQt)
+their work on the SteamDeck)
 
 ## Basic manual setup
 
 Copy this repository file structure into the appropriate places and you'll be
 able to start the session on any Display Manager of your choice.
 
+# User Configuration
+
+The session sources environment from `~/.config/environment.d/*.conf` files.
+The easiest way to configure the session is to create `~/.config/environment.d/gamescope-session-plus.conf`
+and set variables there:
+
+```bash
+# Size of the screen. If not set gamescope will detect native resolution from drm.
+SCREEN_HEIGHT=2160
+SCREEN_WIDTH=3840
+
+# Internal render size of the screen. If not set, will be the same as SCREEN_HEIGHT and SCREEN_WIDTH.
+INTERNAL_WIDTH=1280
+INTERNAL_HEIGHT=800
+
+# Orientation adjustment of panel, possible values: left, right
+ORIENTATION=left
+
+# Enable VRR
+ADAPTIVE_SYNC=1
+
+# Treat the internal panel as an external monitor
+PANEL_TYPE=external
+
+# Set priority of display connectors
+OUTPUT_CONNECTOR='*,DSI-1'
+
+# Set the specific values allowed for refresh rates
+CUSTOM_REFRESH_RATES=40,50,60
+
+# DRM mode generation algorithm (cvt, fixed)
+# TODO: what is this ?
+DRM_MODE=fixed
+```
+
 # License & Contributing
 
 The project is licensed under GPL v3 license. If you want to contribute,