Add audio stream

[Wasmichi]

Thanks for the good example. I got it working from scratch. Could you please add audio streaming ! I think there are only a few lines of code necessary, but I cant get it fixed. I would appreciate that very much.
Greets Wasmichi from Germany

[sonkm3]

Hi, Thank you for stopping by.

Since Raspberry Pi camera does not have audio input capability, I didn't have any care to support audio stream.
(This example intend to use with Raspberry Pi's Camera Module V2 and use its h264 video encoder to make video stream
https://www.raspberrypi.org/products/camera-module-v2/ )

Anyway, I became curious to handle audio track on RTC, I'll make an attempt to that. (Not sure when will it done. ^^)

[sonkm3]

@Wasmichi
Sorry, I took long time to add audio support.

PR #2 would works fine with audio interface.
I tested with USB audio interface, via ALSA.

If you still interested in this, please check them.