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/src/raspbot_v2/setup.py

@@ -10,6 +10,7 @@ setup(
         ('share/ament_index/resource_index/packages', ['resource/' + package_name]),
         ('share/' + package_name, ['package.xml']),
         ('share/' + package_name + '/launch', ['launch/robot.launch.py']),
+        ('share/' + package_name + '/urdf',   ['urdf/raspbot_v2.urdf.xacro']),
     ],
     install_requires=['setuptools'],
     zip_safe=True,