chore: update app.gradle (#91)

Author: vtrifonov

packages/template-drawer-navigation-ts/app/App_Resources/Android/app.gradle

@@ -5,6 +5,10 @@
 //	implementation 'com.android.support:recyclerview-v7:+'
 //}
 
+// If you want to add something to be applied before applying plugins' include.gradle files 
+// e.g. project.ext.googlePlayServicesVersion = "15.0.1"
+// create a file named before-plugins.gradle in the current directory and place it there
+
 android {  
   defaultConfig {  
     generatedDensities = []