Add ShareScreenButton and ShareCameraButton for janus adapter

[vincentfretin]

This is my ShareScreenButton, ShareCameraButton and video system I use with janus adapter.
For now I duplicated index.html to janus.html, you can compare easily the two files.
The example uses video-texture-target and media-frame components from gltf-model-plus, see c-frame/aframe-gltf-model-plus#16

More work to be done to be compatible with easyrtc adapter.

[vincentfretin]

If you want to test locally:

cd janus-plugin-sfu/docker
docker compose up

cd naf-valid-avatars
npm run dev2 # on port 8080

cd naf-janus-adapter
npm start # so it is on 8081

go to https://192.168.1.15:8080/janus.html

[vincentfretin]

For prod, you don't need to run any nodejs server (so no npm start or npm run dev2 command), just use a static build (npm run build) and nginx.