Add Rule.parser property for custom rules to specify which Markdown parser output they use, honor it strictly, and add full type support.

lib/md040.js

@@ -12,6 +12,7 @@ module.exports = {
   "names": [ "MD040", "fenced-code-language" ],
   "description": "Fenced code blocks should have a language specified",
   "tags": [ "code", "language" ],
+  "parser": "micromark",
   "function": function MD040(params, onError) {
     let allowed = params.config.allowed_languages;
     allowed = Array.isArray(allowed) ? allowed : [];