add sticky event support

- use new js-sdk
 - use custom synapse
 - don't filter rooms by existing call state events

Signed-off-by: Timo K <toger5@hotmail.de>

backend/dev_homeserver.yaml

@@ -38,6 +38,8 @@ experimental_features:
   # MSC4222 needed for syncv2 state_after. This allow clients to
   # correctly track the state of the room.
   msc4222_enabled: true
+  # sticky events for matrixRTC user state
+  msc4354_enabled: true
 
 # The maximum allowed duration by which sent events can be delayed, as
 # per MSC4140. Must be a positive value if set.  Defaults to no