Mark app.isReady() as public

docs/api/app.md

@@ -34,7 +34,8 @@ Returns:
 
 Emitted when Electron has finished initialization. On macOS, `launchInfo` holds
 the `userInfo` of the `NSUserNotification` that was used to open the application,
-if it was launched from Notification Center.
+if it was launched from Notification Center. You can call `app.isReady()` to
+check if this event has already fired.
 
 ### Event: 'window-all-closed'
 
@@ -349,6 +350,10 @@ app.relaunch({args: process.argv.slice(1) + ['--relaunch']})
 app.exit(0)
 ```
 
+### `app.isReady()`
+
+Returns `true` if Electron has finished initialization, `false` otherwise.
+
 ### `app.focus()`
 
 On Linux, focuses on the first visible window. On macOS, makes the application