Add rosidl_generator_py to the rosidl_runtime_packages group (#212)

Unlike the c/cpp packages, both generator and runtime facilities are
provided by the same package for Python.

Signed-off-by: Scott K Logan <[email protected]>

Author: cottsay

rosidl_generator_py/package.xml

@@ -71,6 +71,7 @@
   <test_depend>test_interface_files</test_depend>
 
   <member_of_group>rosidl_generator_packages</member_of_group>
+  <member_of_group>rosidl_runtime_packages</member_of_group>
 
   <export>
     <build_type>ament_cmake</build_type>