Add robot definition URDF

This enables rviz2 to know where sensors etc are.
None of the data is correct for the raspbot-v2 yet.

robot/Dockerfile

@@ -7,6 +7,7 @@ SHELL ["/bin/bash", "-c"]
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     python3-colcon-common-extensions \
+    ros-${ROS_DISTRO}-xacro \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /ws
@@ -26,6 +27,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     ros-${ROS_DISTRO}-std-msgs \
     ros-${ROS_DISTRO}-sensor-msgs \
     ros-${ROS_DISTRO}-launch-ros \
+    ros-${ROS_DISTRO}-robot-state-publisher \
+    ros-${ROS_DISTRO}-xacro \
+    ros-${ROS_DISTRO}-tf2-ros \
     python3-smbus \
     && rm -rf /var/lib/apt/lists/*