Add new sample: Mirroring and recording video from camera stream

[stepancar]

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• I have provided steps to reproduce
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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 !!

[stepancar]

Hello @fippo!

I noticed you are reviewing, merging PRs in this repo,
I tried to follow contribution guide to contribute to samples, but didn't get any feedback.
Created this thread https://groups.google.com/g/discuss-webrtc/c/Z-_Pwbm9xP0/m/BwA0d-1sBgAJ but didn't get any feedback there too
This issue has an attached PR.
Could you please validate the idea, and implementation if the idea makes sense?

Thank you!