chore: Swap Gitter with Discord badge

README.md

@@ -15,7 +15,7 @@
 <a href="https://travis-ci.org/nestjs/nest"><img src="https://api.travis-ci.org/nestjs/nest.svg?branch=master" alt="Travis" /></a>
 <a href="https://travis-ci.org/nestjs/nest"><img src="https://img.shields.io/travis/nestjs/nest/master.svg?label=linux" alt="Linux" /></a>
 <a href="https://coveralls.io/github/nestjs/nest?branch=master"><img src="https://coveralls.io/repos/github/nestjs/nest/badge.svg?branch=master#6" alt="Coverage" /></a>
-<a href="https://gitter.im/nestjs/nestjs?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=body_badge"><img src="https://badges.gitter.im/nestjs/nestjs.svg" alt="Gitter" /></a>
+<a href="https://discord.gg/G7Qnnhy" target="_blank"><img src="https://img.shields.io/badge/discord-online-brightgreen.svg" alt="Discord"/></a>
 <a href="https://opencollective.com/nest#backer"><img src="https://opencollective.com/nest/backers/badge.svg" alt="Backers on Open Collective" /></a>
 <a href="https://opencollective.com/nest#sponsor"><img src="https://opencollective.com/nest/sponsors/badge.svg" alt="Sponsors on Open Collective" /></a>
   <a href="https://paypal.me/kamilmysliwiec"><img src="https://img.shields.io/badge/Donate-PayPal-dc3d53.svg"/></a>