Add docs for bottomTab requiring icon on Android (#5619)

Add docs for bottomTab requiring icon on Android

docs/docs/layout-types.md

 }
 ```
 
+!> Note! On Android an `icon` is required when using `bottomTabs`.
+
 ### Selecting tabs programmatically
 
 The selected index is a style property which can be updated using the `mergeOptions` command. In order to update the BottomTabs options, Pass the BottomTabs `componentId` or the `componentId` of one of its children.

lib/src/interfaces/Options.ts

   /**
    * Set the tab icon
    */
-  icon?: ImageRequireSource;
+  icon: ImageRequireSource;
   /**
    * Set the icon tint
    */