title: use sunmi inner printer in ionic
body: <p>i'm trying to use this plugin: <a href="https://github.com/tmalbonph/cordova-plugin-sunmi-inner-printer/" rel="nofollow noreferrer">https://github.com/tmalbonph/cordova-plugin-sunmi-inner-printer/</a></p>
  
  <p>to print with the sunmi device from my ionic app</p>
  
  <p>i declare var sunmiInnerPrinter:any;  before @ionicpage() and then i call sunmiInnerPrinter.methods()</p>
  
  <p>anyway, when calling it, it fails, and i get ' sunmiInnerPrinter is not defined' error</p>
  
  <p>i opened an issue here : <a href="https://github.com/tmalbonph/cordova-plugin-sunmi-inner-printer/issues/1" rel="nofollow noreferrer">https://github.com/tmalbonph/cordova-plugin-sunmi-inner-printer/issues/1</a></p>
  
  <p>how to fix this?</p>