frontends (tools/webrtc): add a options to merge video for PiP and to specify size: - the `merge_pip` option is now used to indicate if local feedback and remote video streams must be merged with local feedback being a PiP of remote video. By default, it's done for `SINKS_AUTO`, but it can be manually specified to use it with `SINKS_APP` or to split ``SINKS_AUTO`` in 2 windows. - target size of the compositor used with `merge_pip` can be specified. By default, 720p is used. rel 428

version: "3.6"
services:

  prosody:
    image: libervia/prosody:demo
    build: prosody-demo

  backend:
    image: libervia/backend:dev-demo
    build: backend-dev-demo

  web:
    image: libervia/web:dev-demo
    build: libervia-web-dev-demo