fix(pointer-events): fix possible undefined stage error

Sometimes a shape may not have a stage associated with it? I was  hitting this in our app. I also cleaned up the event types a bit and added the pointer methods to Stage to be consistent with the other types

src/index-types.d.ts

@@ -46,6 +46,8 @@ declare namespace Konva {
     EventType
   >;
 
+  export type KonvaPointerEvent = import('./PointerEvents').KonvaPointerEvent;
+
   export type KonvaEventListener<
     This,
     EventType