test that the CDN ESM build is importable (to node)

.github/workflows/node.js.yml

@@ -33,6 +33,11 @@ jobs:
       run: |
         npm run test-browser
         node test/builds/browser_build_as_commonjs.js
+    # CDN build should be easily importable
+    - if: contains(matrix.build-how, 'cdn')
+      name: Test: Can import CDN esm build
+      run: |
+        node test/builds/cdn_build_as_esm.mjs
 
     - if: contains(matrix.build-how, 'node')
       name: Test Node.js build

test/builds/cdn_build_as_esm.mjs

@@ -0,0 +1,24 @@
+import hljs from "../../build/es/highlight.js";
+
+const API = [
+  "getLanguage",
+  "registerLanguage",
+  "highlight",
+  "highlightAuto",
+  "highlightAll",
+  "highlightElement"
+];
+
+const assert = (f,msg) => {
+  if (!f()) {
+    console.error(msg);
+    process.exit(1);
+  }
+};
+const keys = Object.keys(hljs);
+
+API.forEach(n => {
+  assert(_ => keys.includes(n), `API should include ${n}`);
+});
+
+console.log("Pass: browser build works with Node.js just fine.")