docs(android): badges fyi for android docs

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

@@ -9,6 +9,8 @@ import { Cordova, IonicNativePlugin, Plugin } from '@ionic-native/core';
  *
  * Requires Cordova plugin: cordova-plugin-badge. For more info, please see the [Badge plugin docs](https://github.com/katzer/cordova-plugin-badge).
  *
+ * Android Note: Badges have historically only been a feature implemented by third party launchers and not visible unless one of those launchers was being used (E.G. Samsung or Nova Launcher) and if enabled by the user. As of Android 8 (Oreo), [notification badges](https://developer.android.com/training/notify-user/badges) were introduced officially to reflect unread notifications. This plugin is unlikely to work as expected on devices running Android 8 or newer. Please see the [local notifications plugin docs](https://github.com/katzer/cordova-plugin-local-notifications) for more information on badge use with notifications.
+ *
  * @usage
  * ```typescript
  * import { Badge } from '@ionic-native/badge/ngx';