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/md047.mjs

@@ -0,0 +1,28 @@
+// @ts-check
+
+import { addError, isBlankLine } from "../helpers/helpers.cjs";
+
+/** @type {import("./markdownlint.mjs").Rule} */
+export default {
+  "names": [ "MD047", "single-trailing-newline" ],
+  "description": "Files should end with a single newline character",
+  "tags": [ "blank_lines" ],
+  "parser": "none",
+  "function": function MD047(params, onError) {
+    const lastLineNumber = params.lines.length;
+    const lastLine = params.lines[lastLineNumber - 1];
+    if (!isBlankLine(lastLine)) {
+      addError(
+        onError,
+        lastLineNumber,
+        undefined,
+        undefined,
+        [ lastLine.length, 1 ],
+        {
+          "insertText": "\n",
+          "editColumn": lastLine.length + 1
+        }
+      );
+    }
+  }
+};