Add community engagement badges
[![GitHub Release Date](https://img.shields.io/github/release-date/contiki-ng/contiki-ng.svg)](https://github.com/contiki-ng/contiki-ng/releases/latest)
[![Last commit](https://img.shields.io/github/last-commit/contiki-ng/contiki-ng.svg)](https://github.com/contiki-ng/contiki-ng/commit/HEAD)
+[![Stack Overflow Tag](https://img.shields.io/badge/Stack%20Overflow%20tag-Contiki--NG-blue?logo=stackoverflow)](https://stackoverflow.com/questions/tagged/contiki-ng)
+[![Gitter](https://img.shields.io/badge/Gitter-Contiki--NG-blue?logo=gitter)](https://gitter.im/contiki-ng)
+[![Twitter](https://img.shields.io/badge/Twitter-%40contiki__ng-blue?logo=twitter)](https://twitter.com/contiki_ng)
+
Contiki-NG is an open-source, cross-platform operating system for Next-Generation IoT devices. It focuses on dependable (secure and reliable) low-power communication and standard protocols, such as IPv6/6LoWPAN, 6TiSCH, RPL, and CoAP. Contiki-NG comes with extensive documentation, tutorials, a roadmap, release cycle, and well-defined development flow for smooth integration of community contributions.
Unless explicitly stated otherwise, Contiki-NG sources are distributed under
