fix: make PickerItemProps accept generic value rather than just ItemValue (#302)

Author: Dor256

typings/Picker.d.ts

@@ -113,7 +113,7 @@ declare class Picker<T> extends React.Component<PickerProps<T>, {}> {
    */
   static readonly MODE_DROPDOWN: 'dropdown';
 
-  static Item: React.ComponentType<PickerItemProps<ItemValue>>;
+  static Item: React.ComponentType<PickerItemProps<T>>;
 
   /**
    * @platform android