Specify devices at top of non-file streaming scripts

This makes it clearer to end users how to select devices. It's too cumbersome to do this at the command line I think, else they'd just use plain FFmpeg instead of this thin wrapper.

Endless -loop option for globbed file lists

v1.0.2

doc [ci skip]

Documentation, audio streaming with static image

v1.0.1

selftest

Initially working

Works for

• stream existing video files by globbing in directory
• stream existing video file in endless loop
• webcam stream
• screenshare stream