♻️(y-provider) replace y-webrtc-signaling by server-y-provider

We replace the y-webrtc-signaling app by
the server-y-provider server.
The server-y-provider server uses @hocuspocus to
do collaborative editing on docs.

src/frontend/servers/y-provider/nodemon.json

@@ -0,0 +1,5 @@
+{
+  "watch": ["src"],
+  "ext": "ts",
+  "exec": "yarn build"
+}