Fix label of Slack channel badge

Author: alranel

README.md

@@ -2,7 +2,7 @@
 
 ![Repo Status:
 Alpha](https://img.shields.io/badge/status-alpha-lightgrey.svg?longCache=true&style=plastic)
-[![Join the #publiccode channel](https://img.shields.io/badge/Slack%20channel-%23design-blue.svg)](https://developersitalia.slack.com/messages/CAM3F785T/)
+[![Join the #publiccode channel](https://img.shields.io/badge/Slack%20channel-%23publiccode-blue.svg)](https://developersitalia.slack.com/messages/CAM3F785T)
 [![Get invited](https://slack.developers.italia.it/badge.svg)](https://slack.developers.italia.it/)
 
 A metadata description standard for public software and policy repositories