Incorporate height into the GroundItems overlay

runelite-api/src/main/java/net/runelite/api/ItemLayer.java

@@ -26,6 +26,8 @@ package net.runelite.api;
 
 public interface ItemLayer extends TileObject
 {
+	int getHeight();
+
 	Renderable getBottom();
 
 	Renderable getMiddle();

runelite-api/src/main/java/net/runelite/api/TileObject.java

@@ -45,6 +45,8 @@ public interface TileObject
 
 	Point getCanvasLocation();
 
+	Point getCanvasLocation(int zOffset);
+
 	Polygon getCanvasTilePoly();
 
 	Point getCanvasTextLocation(Graphics2D graphics, String text, int zOffset);