Initialise flipper-ui-browser with socket connection

Summary:
This diff sets up the socket connection between flipper-browser and flipper-server, and verifies that the initial UI initialisation work (e.g. `get-config` command works). The initial RenderHost is initialised as well based on the config and browser APIs.

Note that flipper-ui-core itself isn't started yet, as that has still a plethora of node imports, so Metro will correctly refuse to bundle

Not in this diff
* remove Node usage from flipper-ui-core
* implement all RenderHost APIs

Reviewed By: aigoncharov

Differential Revision: D32644074

fbshipit-source-id: 2c8065caf0191771a3867b69a431ca50eeb7a5a3

desktop/flipper-server/src/startBaseServer.tsx

@@ -64,12 +64,7 @@ function startAssetServer(
 }
 
 function addWebsocket(server: http.Server) {
-  const io = new socketio.Server(server); // 3.1.0 socket.io doesn't have type definitions
-
-  io.on('connection', (client) => {
-    console.log(chalk.green(`Client connected ${client.id}`));
-  });
-
+  const io = new socketio.Server(server);
   return io;
 }