Add RTFD docs jobs for active craton projects

Craton and python-cratonclient have been looking for to properly publish
their documentation.

Prior to moving to OpenStack's infrastructure, Craton was published on
RTFD: https://craton.readthedocs.io/en/latest/ and now we hope to
publish python-cratonclient to
https://cratonclient.readthedocs.io/en/latest/

Change-Id: I88b8fa75a1c1397aac4cde5d430fc07d6786b586

jenkins/jobs/projects.yaml

@@ -1497,6 +1497,7 @@
     name: craton
 
     jobs:
+      - hook-{name}-rtfd
       - 'gate-{name}-python35'
       - 'gate-{name}-docs-{node}':
           node: ubuntu-xenial
@@ -12312,6 +12313,7 @@
     name: python-cratonclient
 
     jobs:
+      - hook-{name}-rtfd
       - python-jobs
 
 - project:

zuul/layout.yaml

@@ -6973,6 +6973,7 @@ projects:
     template:
       - name: merge-check
       - name: python35-jobs
+      - name: docs-on-rtfd
     check:
       - gate-craton-pep8-ubuntu-xenial
       - gate-craton-docs-ubuntu-xenial
@@ -15953,6 +15954,7 @@ projects:
       - name: python-jobs
       - name: python35-jobs
       - name: check-requirements
+      - name: docs-on-rtfd
 
   - name: openstack/python-cueclient
     template: