message: Update readme, add discord badge&link
diff: ------------------
  ![UI for Apache Kafka Price Free](images/free-open-source.svg)
  +[![Chat with us](https://img.shields.io/discord/897805035122077716)](https://discord.gg/4DWzD7pGE5)
  <em>UI for Apache Kafka is a free, open-source web UI to monitor and manage Apache Kafka clusters. </em>
  