merge respective .luacheckrc files and move redundant license file

.luacheckrc

@@ -1,3 +1,5 @@
 globals = {
-    "sound_api", "minetest",
+    "sound_api", "minetest", "mcl_sounds", "default", "ks_sounds",
+    "nodes_nature", "fl_stone", "fl_topsoil", "fl_trees",
+    "hades_sounds", "rp_sounds",
 }