[Feature] Underworld Command auto return

- Add #underworld to list out all underworld mobs
- Add automatic return to spawn on underworld mobs

zone/gm_commands/underworld.cpp

@@ -0,0 +1,5 @@
+#include "../client.h"
+
+void command_underworld(Client *c, const Seperator *sep) {
+	entity_list.GetUnderworldMobs(c);
+}