[Feature] FreeBSD support (general info)

[cytopia]

Support help here: https://forums.freebsd.org/threads/ffmpeg-x11grab-and-v4l2-ctl.54464/

Make it work under FreeBSD

Required tools:

• multimedia/ffmpeg
• x11/xgrab
• multimedia/libv4l
• multimedia/v4l-utils
• x11/xdpyinfo

Current work will be done in branch feature/freebsd