Fixed indentation on readme

Author: codepr

README.md

@@ -107,7 +107,7 @@ To get started, simply fork this repo. Please refer to [CONTRIBUTING.md](CONTRIB
   - [Part 5 - Redis case study](https://eli.thegreenplace.net/2017/concurrent-servers-part-5-redis-case-study/)
   - [Part 6 - Callbacks, Promises and async/await](https://eli.thegreenplace.net/2018/concurrent-servers-part-6-callbacks-promises-and-asyncawait/)
 
- - MQTT Broker from scratch
+- MQTT Broker from scratch
   - [Part 1 - The protocol](https://codepr.github.io/posts/sol-mqtt-broker)
   - [Part 2 - Networking](https://codepr.github.io/posts/sol-mqtt-broker-p2)
   - [Part 3 - Server](https://codepr.github.io/posts/sol-mqtt-broker-p3)