[Octoprint] - webcam support

[TheLankyScottishNerd]

I'm not sure if this has come up before but it would seem webcams do not work in the current Octoprint setup, which for long prints and some of the AI print monitoring plugins is simply a must have for some printers like myself.

Looking at the docker compose it may be missing the "Environment" section. A working docker-compose.yaml has the following sections:

devices:
- /dev/ttyUSB0:/dev/ttyUSB0
- /dev/video0:/dev/video0
volumes:
- octoprint:/octoprint
environment:
- ENABLE_MJPG_STREAMER=true
- MJPG_STREAMER_INPUT=-r 1920x1080 -f 30 -y

I can see that the docker-compose.yaml is different when deployed on Umbrel and the devices are taken care of by included the entire /dev mount but I think adding the Environment section would resolve the cameras not working in OctoPrint and specifying the path to ffmpeg inside the Octoprint application to '/usr/bin/ffmpeg'.

I'm not sure if anything else is required but this is the difference I see between the Umbrel deployment and a working Docker deployment.