Add #timeout param for ffmpeg source

[felipecrs]

This PR adds the #timeout parameter to the FFmpeg source, similar to the #timeout parameter of the RTSP source.

It allows users to easily modify the timeout value for RTSP inputs per stream without the need of copying all the other parameters using #input=.

Also, it makes the global default timeout configurable in a similar manner. It still defaults to 5 seconds.

Example:

ffmpeg:
  timeout: 10  # you can override it here for all streams

streams:
  # or you can override per-stream too
  mycam: ffmpeg:rtsp://192.168.1.33/0/av0#timeout=15#video=copy#audio=copy

[AlexxIT]

Thanks!

[AlexxIT]

https://github.com/AlexxIT/go2rtc/releases/tag/v1.9.14