Mention roadmap in the README

Author: mickel8

README.md

@@ -44,6 +44,7 @@ To get started with Elixir WebRTC, check out:
 * the [examples directory](https://github.com/elixir-webrtc/ex_webrtc/tree/master/examples) that contains a bunch of very simple usage examples of the library
 * the [`apps` repo](https://github.com/elixir-webrtc/apps) with example applications built on top of `ex_webrtc`
 * the [documentation](https://hexdocs.pm/ex_webrtc/readme.html), especially the [`PeerConnection` module page](https://hexdocs.pm/ex_webrtc/ExWebRTC.PeerConnection.html)
+* the [roadmap](https://github.com/elixir-webrtc/ex_webrtc/issues/28) to see what we are working on and how you can contribute
 
 If you have any questions, ideas or topics to discuss about Elixir WebRTC, head to the [discussions page](https://github.com/orgs/elixir-webrtc/discussions).