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

lib/md009.js

@@ -12,6 +12,7 @@ module.exports = {
   "names": [ "MD009", "no-trailing-spaces" ],
   "description": "Trailing spaces",
   "tags": [ "whitespace" ],
+  "parser": "markdownit",
   "function": function MD009(params, onError) {
     let brSpaces = params.config.br_spaces;
     brSpaces = Number((brSpaces === undefined) ? 2 : brSpaces);