Add in python3-dev build dependency (#334)

We need this because we call find_package(Python3 Development) in our CMakeLists.txt here.

Signed-off-by: Chris Lalancette <[email protected]>

image_transport_py/package.xml

@@ -19,6 +19,7 @@
   <buildtool_depend>ament_cmake_python</buildtool_depend>
 
   <build_depend>pybind11_vendor</build_depend>
+  <build_depend>python3-dev</build_depend>
 
   <depend>image_transport</depend>
   <depend>rclcpp</depend>