fix(core): conditionally include hostname parameter when using dete…

…ct port

- Skip adding the `hostname` parameter if the host is "localhost".

packages/docusaurus/src/server/getHostPort.ts

@@ -54,7 +54,10 @@ async function choosePort(
   defaultPort: number,
 ): Promise<number | null> {
   try {
-    const port = await detect({port: defaultPort, hostname: host});
+    const port = await detect({
+      port: defaultPort,
+      ...(host !== 'localhost' && {hostname: host}),
+    });
     if (port === defaultPort) {
       return port;
     }