add doc for project neutron-fwaas

Neutron drivers team discussed the topic of the maintenance of
neutron-fwaas, and agreed to include neutron-fwaas again to Neutron
stadium[1].

the governance change merged[2]

[1] https://meetings.opendev.org/meetings/neutron_drivers/2022/neutron_drivers.2022-01-28-14.00.log.html#l-14
[2] https://review.opendev.org/c/openstack/governance/+/828078

Change-Id: I5de59949fb72cd3711586dd333596dc7d0184e0f

www/project-data/latest.yaml

@@ -115,6 +115,9 @@
   type: networking
   has_install_guide: true
   has_admin_guide: true
+- name: neutron-fwaas
+  service: Firewall-as-a-Service Plug-in
+  type: networking
 - name: neutron-vpnaas
   service: VPN-as-a-Service Plug-in
   type: networking