Add new sample: Mirroring and recording video from camera stream

[stepancar]

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Description

Hello!
I want to add new sample which demonstrates mirroring video stream from camera and recording with media encoder.
In that sample I want to highlight difference between processing video in main thread and in web worker.

This is a prototype
https://stepancar.github.io/webrtc-samples/src/content/insertable-streams/video-recording/

Any concerns?

[crizmo]

Thanks !!