Add isHeadless attribute to scribe messages

Summary:
So we can distinguish between humans and the machines.

We can redirect the traffic to different tables based on this attribute if necessary.

Reviewed By: danielbuechele

Differential Revision: D14025004

fbshipit-source-id: c3a24b5f8a30f24445eaee67843b78ddabfc9d51

headless/index.js

@@ -94,7 +94,7 @@ function startFlipper({
         devToolsEnhancer({realtime: true, hostname: 'localhost', port: 8181}),
       )
     : createStore(reducers);
-  const logger = new Logger(store);
+  const logger = new Logger(store, {isHeadless: true});
   init(store);
   dispatcher(store, logger);