ADD CONTRIBUTING for networking-vpp

Change-Id: I8429f00484181ddba8f55ec0ec43674339d5672a

CONTRIBUTING.rst

@@ -0,0 +1,17 @@
+If you would like to contribute to the development of OpenStack, you must
+follow the steps in this page:
+
+   https://docs.openstack.org/infra/manual/developers.html
+
+If you already have a good understanding of how the system works and your
+OpenStack accounts are set up, you can skip to the development workflow
+section of this documentation to learn how changes to OpenStack should be
+submitted for review via the Gerrit tool:
+
+   https://docs.openstack.org/infra/manual/developers.html#development-workflow
+
+Pull requests submitted through GitHub will be ignored.
+
+Bugs should be filed on Launchpad, not GitHub:
+
+   https://bugs.launchpad.net/networking-vpp