docs: update installation guide (#541)

Author: rachwalk

README.md

@@ -79,6 +79,8 @@ Currently, docker images are experimental. See the [docker](docs/setup_docker.md
 ## Setup (local)
 
 Before going further, make sure you have ROS 2 (Jazzy or Humble) installed and sourced on your system.
+If you don't have ROS 2 follow the installation documentation for [Humble](https://docs.ros.org/en/humble/Installation/Ubuntu-Install-Debs.html) or [Jazzy](https://docs.ros.org/en/jazzy/Installation/Ubuntu-Install-Debs.html).
+Make sure that `ros-dev-tools` are installed.
 
 ### 1. Setting up the workspace: