Changed screen capture to non effect. Effects are used to alter the stream, this feature does not need to alter the stream, it just needs access to it

Changed image diff library. Previous library diff’ed the whole image, the new one has en early return threshold

Use ImageCaptureAPI to take the screenshot. Added polyfill for it and polyfill for createImageBitmap

Added analytics

This effect doesn't modify the media stream, so its safe to start/stop effect and not apply it on the JitsiLocalTrack. This way we can make sure that this effect is not switched out when presenter effect is applied.