support creality webrtc camera

Author: springhack

creality-discovery/README.md

@@ -3,8 +3,12 @@
 ### Config Envs
 - `CR_ID`: printer id, eg: `1234567890ABCD`
 - `CR_IFACE`: which network interface to scan
-- `CR_PORTS`: tcp ports to forward, eg: `4408,8000`
+- `CR_PORTS`: tcp ports to forward, eg: `4408`
 - `CR_INTERVAL`: how often to scan, eg: `10`
+- `CR_CAMERA`: enable camera WebRTC relay on port `8000`, default: `true`
+
+When `CR_CAMERA` is enabled, open `http://<host>:8000` to view the printer
+camera. It forwards WebRTC traffic to `http://<printer-ip>:8000/call/webrtc_local`.
 
 ### Get `CR_ID`
 > Servel ways, eg: mobile app info, ssh or `Creality Print` desktip client