refactor: optimize plugins for angular treeshaking

BREAKING CHANGE: You can remove the plugin import from the app.module.ts because of the changed Inject decorator

src/@ionic-native/plugins/toast/index.ts

@@ -67,7 +67,9 @@ export interface ToastOptions {
   repo: 'https://github.com/EddyVerbruggen/Toast-PhoneGap-Plugin',
   platforms: ['Android', 'BlackBerry 10', 'iOS', 'Windows', 'Windows Phone 8']
 })
-@Injectable()
+@Injectable({
+  providedIn: 'root'
+})
 export class Toast extends IonicNativePlugin {
   /**
    * Show a native toast for the given duration at the specified position.