title: How to launch a OneSignal prompt while using ionic?
body: <p>The OneSignal site goes through great detail on launching the prompt for browsers, but I'm either overlooking the option for mobile or that option doesn't exist.</p>
  
  <p>I'm using Ionic 4/Angular 8 with the cordova-onesignal plugin. I've tried <code>OneSignal.showNativePrompt()</code> but that method doesn't exist on OneSignal. I've also tried <code>this.oneSignal</code> just to see what functions are available and read the comments, but there doesn't seem to be anything that triggers the prompt. </p>
  
  <p>Is there some other way using Ionic to trigger the message to allow users to subscribe to notifications?</p>