fix(entity): initialize Module_Doc List properties

src/awesomewm.d.tl/entity/Module_Doc.tl

@@ -18,7 +18,13 @@ end
 
 local __Module_Doc: metatable<Module_Doc> = {
    __call = function(_: Module_Doc): Module_Doc
-      return {}
+      return {
+         constructors = List(),
+         methods = List(),
+         properties = List(),
+         static_functions = List(),
+         signals = List(),
+      }
    end,
 }