Update README.rst
Added missing file links.
@@ -467,4 +467,8 @@ Contributing
.. _motohawk_no_floating_point_numbers.c: https://github.com/eerimoq/cantools/blob/master/tests/files/c_source/motohawk_no_floating_point_numbers.c
+.. _motohawk_sender_node.h: https://github.com/eerimoq/cantools/blob/master/tests/files/c_source/motohawk_sender_node.h
+
+.. _motohawk_sender_node.c: https://github.com/eerimoq/cantools/blob/master/tests/files/c_source/motohawk_sender_node.c
+
.. _matplotlib: https://matplotlib.org/
