Convert markdownlint library to an ECMAScript module, replace markdownlint-micromark with micromark, stop publishing (large) markdownlint-browser.js, see https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c for guidance.

lib/md036.mjs

@@ -0,0 +1,42 @@
+// @ts-check
+
+import { addErrorContext, allPunctuation } from "../helpers/helpers.cjs";
+import { getDescendantsByType } from "../helpers/micromark-helpers.cjs";
+import { filterByTypesCached } from "./cache.mjs";
+
+/** @typedef {import("../helpers/micromark-helpers.cjs").TokenType} TokenType */
+/** @type {TokenType[][]} */
+const emphasisTypes = [
+  [ "emphasis", "emphasisText" ],
+  [ "strong", "strongText" ]
+];
+
+/** @type {import("./markdownlint.mjs").Rule} */
+export default {
+  "names": [ "MD036", "no-emphasis-as-heading" ],
+  "description": "Emphasis used instead of a heading",
+  "tags": [ "headings", "emphasis" ],
+  "parser": "micromark",
+  "function": function MD036(params, onError) {
+    let punctuation = params.config.punctuation;
+    punctuation = String((punctuation === undefined) ? allPunctuation : punctuation);
+    const punctuationRe = new RegExp("[" + punctuation + "]$");
+    const paragraphTokens =
+      filterByTypesCached([ "paragraph" ])
+        .filter((token) =>
+          (token.parent?.type === "content") && !token.parent?.parent && (token.children.length === 1)
+        );
+    for (const emphasisType of emphasisTypes) {
+      const textTokens = getDescendantsByType(paragraphTokens, emphasisType);
+      for (const textToken of textTokens) {
+        if (
+          (textToken.children.length === 1) &&
+          (textToken.children[0].type === "data") &&
+          !punctuationRe.test(textToken.text)
+        ) {
+          addErrorContext(onError, textToken.startLine, textToken.text);
+        }
+      }
+    }
+  }
+};