Broaden notification message type definition

Summary:
Let's the notification render any React node.
Particularly useful when including links or wanting to
format messages.

Reviewed By: jknoxville

Differential Revision: D10488157

fbshipit-source-id: 06d3c6b4477c78e8bef78e3a3dc0e05bc67a2ef4

src/plugin.js

@@ -11,6 +11,7 @@ import type Logger from './fb-stubs/Logger.js';
 import type Client from './Client.js';
 
 import React from 'react';
+import type {Node} from 'react';
 import BaseDevice from './devices/BaseDevice.js';
 import {AndroidDevice, IOSDevice} from 'flipper';
 
@@ -27,7 +28,7 @@ type PluginTarget = BaseDevice | Client;
 export type Notification = {|
   id: string,
   title: string,
-  message: string,
+  message: string | Node,
   severity: 'warning' | 'error',
   timestamp?: number,
   category?: string,