implement generic broadcastchannel and apply it to websocket provider

examples/exampleConfig.js

@@ -0,0 +1,9 @@
+/* eslint-env browser */
+
+const isDeployed = location.hostname === 'yjs.website'
+
+if (!isDeployed) {
+  console.log('%cYjs: Start your local websocket server by running %c`npm run websocket-server`', 'color:blue', 'color: grey; font-weight: bold')
+}
+
+export const serverAddress = isDeployed ? 'wss://api.yjs.website' : 'ws://localhost:1234'