Add --launcher-msg option to pass to desktop app

Summary:
Allows the launcher to provide messages to the user. Currently, in the form
of the red notification bar at the bottom. This is just meant as a temporary measure
during the alpha to have some clearly noticeable way of getting the user's attention.

I consider removing this a blocker for the release as this mechanism is not well
suited for this in many ways.

The current use case for this is providing a warning if a cached version is used
instead of the requested one, e.g. "Could not fetch requested Flipper version 'deadbeef', using cached version instead."

Reviewed By: jknoxville, priteshrnandgaonkar

Differential Revision: D14073687

fbshipit-source-id: 85630347027063103315eeb1286731fe2478e261

src/init.js

@@ -18,6 +18,8 @@ import {persistStore} from 'redux-persist';
 import reducers from './reducers/index.js';
 import dispatcher from './dispatcher/index.js';
 import TooltipProvider from './ui/components/TooltipProvider.js';
+import config from './utils/processConfig.js';
+import {initLauncherHooks} from './utils/launcher.js';
 const path = require('path');
 
 const store = createStore(
@@ -55,6 +57,8 @@ function init() {
       (r.installing || r.active).postMessage({precachedIcons});
     })
     .catch(console.error);
+
+  initLauncherHooks(config(), store);
 }
 
 // make init function callable from outside