Switch to Web test runner

.github/workflows/test.yml

@@ -0,0 +1,11 @@
+name: Test
+on: ["push", "pull_request"]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-node@v4
+    - run: npm ci
+    - run: npm test
+    - uses: coverallsapp/github-action@v2

callback.js → callback.mjs

@@ -1,6 +1,6 @@
 var count = 0;
 
-module.exports = function (url, options, callback) {
+export default function (url, options, callback) {
   if (!callback) {
     callback = options;
     options = {};