Enable jsdoc/require-jsdoc rule, fix all violations (fixes #85).

lib/md004.js

@@ -3,22 +3,9 @@
 "use strict";
 
 const { addErrorDetailIf, listItemMarkerRe,
-  rangeFromRegExp } = require("../helpers");
+  rangeFromRegExp, unorderedListStyleFor } = require("../helpers");
 const { flattenedLists } = require("./cache");
 
-// Returns the unordered list style for a list item token
-function unorderedListStyleFor(token) {
-  switch (token.markup) {
-    case "-":
-      return "dash";
-    case "+":
-      return "plus";
-    // case "*":
-    default:
-      return "asterisk";
-  }
-}
-
 module.exports = {
   "names": [ "MD004", "ul-style" ],
   "description": "Unordered list style",