fix(package): update cordova-android to version 8.1.0

Closes #15

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
         "@ionic-native/status-bar": "^4.5.2",
         "@ionic/storage": "^2.1.3",
         "build": "0.1.4",
-        "cordova-android": "^7.0.0",
+        "cordova-android": "^8.1.0",
         "cordova-ios": "^4.5.4",
         "cordova-plugin-device": "^2.0.1",
         "cordova-plugin-ionic-webview": "^1.1.16",