[Netlify] Add sticky event support

[toger5]

Do not merge, this is just there for a netlfify build.

• use new js-sdk Sticky Events support for matrixRTC (MSC4354) matrix-org/matrix-js-sdk#5017
• use custom synapse
• don't filter rooms by existing call state events
• enable the stickyEvent option in the joinConfig

To test:
Option 1:

• use the linked netlify build https://pr3513--element-call.netlify.app/
• open the netlify url WITH a homeserver url parameter to link your custom homeserver (example: https://localhost:3000?homeserver=https%3A%2F%2Ftest.com encoding is of course needed)
• start a call with this link (using the homeserver url param) (in multiple browser envs (private, non private OR firefox container extension)

Option 2:
pull/download this PR/branch
start the docker dev env via yarn backend (synapse, livekit sfu, nginx, jwt authorizationService...)
(in a new terminal) start EC yarn dev

Now it should "just work" to do calls on https://localhost:3000