Wiki doesn't document how to use new libtgsconverter

[BenWiederhake]

Describe the bug

I've seen #1569, but by reading the code I don't understand how to make sure that the new libtgsconverter is used.

To Reproduce

• Open and read https://github.com/42wim/matterbridge/wiki/Settings#mediaConverttgs

Expected behavior

• Text appears that says something like To choose the backend, use either `LottieBackend=lottie_convert` or `LottieBackend=libtgsconvert`.

Additional context Thank you very much for #1569, I just don't grok how to switch backends :D

CC @Benau