add luacheck

.luacheckrc

@@ -0,0 +1,8 @@
+-- based on https://gitea.your-land.de/your-land/bugtracker/wiki/luacheck%2C-stylua%2C-pre-commit
+
+std = "lua51+chat_formspec"
+
+stds.chat_formspec = {
+    read_globals = {"minetest"},
+    globals = {"chat_formspec"}
+}