Use static JSON key as NPC ID for NPCs and mobs

src/TableData.hpp

@@ -3,6 +3,11 @@
 
 #include "NPCManager.hpp"
 
+// these are added to the NPC's static key to avoid collisions
+const int NPC_ID_OFFSET = 0;
+const int MOB_ID_OFFSET = 10000;
+const int MOB_GROUP_ID_OFFSET = 20000;
+
 // typedef for JSON object because I don't want to type nlohmann::json every time
 typedef nlohmann::json json;