Use webpack to create a CommonJS module from micromark's ESM implementation, convert to using that.

micromark/webpack.config.js

@@ -0,0 +1,34 @@
+// @ts-check
+
+"use strict";
+
+const shared = {
+  "entry": "./exports.mjs",
+  "output": {
+    "library": {
+      "type": "commonjs"
+    },
+    "path": __dirname
+  },
+  "target": "node"
+};
+
+module.exports = [
+  {
+    ...shared,
+    "mode": "production",
+    "output": {
+      ...shared.output,
+      "filename": "micromark.js"
+    }
+  },
+  {
+    ...shared,
+    "devtool": false,
+    "mode": "development",
+    "output": {
+      ...shared.output,
+      "filename": "micromark.dev.js"
+    }
+  }
+];