disconnect in basic example (#2235)

Author: reviewher

README.md

@@ -52,6 +52,7 @@ await client.connect();
 
 await client.set('key', 'value');
 const value = await client.get('key');
+await client.disconnect();
 ```
 
 The above code connects to localhost on port 6379. To connect to a different host or port, use a connection string in the format `redis[s]://[[username][:password]@][host][:port][/db-number]`: