migrate to victoria testing runtime

As per victoria cycle testing runtime and community goal[1]
we need to migrate upstream CI/CD to Ubuntu Focal(20.04)
and Node.js 10.

Also switch from oslosphinx to openstackdocstheme

Depends-On: https://review.opendev.org/#/c/738328/
Story: #2007865
Task: #40212

[1] https://governance.openstack.org/tc/goals/selected/victoria/migrate-ci-cd-jobs-to-ubuntu-focal.html

Change-Id: I7cfdfb11869ac90244561d34d1f4fdf26a5e8ad0

.zuul.yaml

@@ -1,4 +1,15 @@
 - project:
     templates:
-      - nodejs4-jobs
-      - nodejs8-docs
+      - nodejs10-jobs
+    check:
+      jobs:
+        - nodejs-npm-run-docs:
+            vars:
+              node_version: 10
+            nodeset: ubuntu-focal
+    gate:
+      jobs:
+        - nodejs-npm-run-docs:
+            vars:
+              node_version: 10
+            nodeset: ubuntu-focal

doc/source/conf.py

@@ -34,6 +34,14 @@ openstackdocs_pdf_link = True
 # text edit cycles.
 # execute "export SPHINX_DEBUG=1" in your terminal to disable
 
+# openstackdocstheme options
+repository_name = 'openstack/eslint-config-openstack'
+bug_project = 'eslint-config-openstack'
+bug_tag = ''
+
+# Must set this variable to include year, month, day, hours, and minutes.
+html_last_updated_fmt = '%Y-%m-%d %H:%M'
+
 # The suffix of source filenames.
 source_suffix = '.rst'