chore: update gitignore and add note in README (#311)

Signed-off-by: tison <wander4096@gmail.com>
diff --git a/.gitignore b/.gitignore
index b6ad8df..cd28973 100644
--- a/.gitignore
+++ b/.gitignore
@@ -25,5 +25,6 @@
 *.tar.gz
 *.tgz
 pkg/linux/pulsar-cpp/
+pkg/mac/build-pulsar/
 lib/
 src/cert.pem
diff --git a/README.md b/README.md
index 56b19bb..e51dbd0 100644
--- a/README.md
+++ b/README.md
@@ -73,7 +73,7 @@
     data: Buffer.from("hello")
   });
 
-  // Receive the message 
+  // Receive the message
   const msg = await consumer.receive();
   console.log(msg.getData().toString());
   consumer.acknowledge(msg);
@@ -134,6 +134,10 @@
 
 To verify it has been installed successfully, you can run an example like:
 
+> **Note**
+>
+> A running Pulsar server is required. The example uses `pulsar://localhost:6650` to connect to the server.
+
 ```shell
 node examples/producer
 ```