Add loot to dungeons (#1921)

mods/dungeon_loot/README.txt

@@ -0,0 +1,11 @@
+Minetest Game mod: dungeon_loot
+===============================
+Adds randomly generated chests with some "loot" to generated dungeons,
+an API to register additional loot is provided.
+Only works if dungeons are actually enabled in mapgen flags.
+
+License information can be found in license.txt
+
+Authors of source code
+----------------------
+Originally by sfan5 (MIT)