test: listen on ::1 (#60)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
	- Introduced a detection functionality for identifying available ports.
	- Created a new server instance listening on port 7001.
	- Added a test case to verify detection of the next available port.

- **Bug Fixes**
	- Implemented error handling for server startup issues.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

test/demo/detect.js

@@ -0,0 +1,9 @@
+import { detect } from '../../dist/esm/index.js';
+
+detect(7001)
+  .then(port => {
+    console.log(port);
+  })
+  .catch(err => {
+    console.error(err);
+  });

test/demo/server.js

@@ -0,0 +1,8 @@
+import { createServer } from 'node:http';
+import { hostname } from 'node:os';
+
+const server = createServer();
+
+server.listen(7001, hostname(), () => {
+  console.log('listening %s:7001, address: %o', hostname(), server.address());
+});

test/detect-port.test.ts

@@ -44,6 +44,13 @@ describe('test/detect-port.test.ts', () => {
       });
       servers.push(server4);
 
+      const server5 = new net.Server();
+      server5.listen(25500, '::1', cb);
+      server5.on('error', err => {
+        console.error('listen ::1 error:', err);
+      });
+      servers.push(server5);
+
       for (let port = 27000; port < 27010; port++) {
         const server = new net.Server();
         if (port % 3 === 0) {
@@ -102,6 +109,13 @@ describe('test/detect-port.test.ts', () => {
       assert.equal(realPort, 25001);
     });
 
+    it('work with listening next port 25501 because 25500 was listened to ::1', async () => {
+      const port = 25500;
+      const realPort = await detectPort(port);
+      assert(realPort);
+      assert.equal(realPort, 25501);
+    });
+
     it('should listen next port 24001 when localhost is not binding', async () => {
       mm(dns, 'lookup', (...args: any[]) => {
         mm.restore();