replace gitter to discord on the main page

Author: nmarticorena

docs/index.md

@@ -33,10 +33,10 @@ See [Getting Started](https://robostack.github.io/GettingStarted.html)
 Please see the "Available Packages" links in the menu. If a package is not yet available for a given distribution/platforms, simply open a pull request and we will do our best to get it up any running.
 
 ## How to get involved?
-We are very keen to involve more collaborators. Join us on [Gitter](https://gitter.im/RoboStack/Lobby) and check out our [Contribution guidelines](https://robostack.github.io/Contributing.html).
+We are very keen to involve more collaborators. Join us on [`robotics` channel on `prefix.dev`'s discord](https://discord.gg/kKV8ZxyzY4) and check out our [Contribution guidelines](https://robostack.github.io/Contributing.html).
 
 ## Overview video
 Check out our IROS 2022 presentation for a 7 minute teaser:
 <div class="video-wrapper">
 <iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/QJE9a1zCSRM" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>
-</div>
+</div>