Expose environment info

Summary: The part I'm most interested in is the `appVersion`. For non-debug builds this will allow us to check if a flipper-server version is compatible with flipperd/arc_uiqr or any other tool that builds on top of it.

Reviewed By: lblasa

Differential Revision: D37456699

fbshipit-source-id: 50eeb6da0f55e3a3552d43fa7c9ea34608090f97

desktop/flipper-server-core/src/FlipperServerImpl.tsx

@@ -489,6 +489,9 @@ export class FlipperServerImpl implements FlipperServer {
         return false;
       }
     },
+    'environment-info': async () => {
+      return this.config.environmentInfo;
+    },
   };
 
   registerDevice(device: ServerDevice) {