Flag npc as dead when their health ratio hits 0

Sometimes npcs despawn without their HP var visible after death

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

@@ -65,4 +65,11 @@ public interface NPC extends Actor
 	 * @return the transformed NPC
 	 */
 	NPCComposition getTransformedComposition();
+
+	/**
+	 * Returns true if this NPC has died
+	 *
+	 * @return
+	 */
+	boolean isDead();
 }