Jsonnet examples

It is probably not elegant or idiomatic jsonnet. I am learning Jsonnet.

I believe the explanation is correct, but I still have to retry this
example for repeatability and check for completeness.

* Jsonnet example - gutted

* take some personalize things away
* clean up awkward sentence
* for real gitops

Signed-off-by: Kingdon Barrett <kingdon@weave.works>

mkdocs.yml

@@ -66,6 +66,7 @@ nav:
       - Sortable image tags to use with automation: guides/sortable-image-tags.md
   - Use Cases:
       - Azure: use-cases/azure.md
+      - GitHub Actions Manifest Generation: use-cases/gh-actions-manifest-generation.md
       - Helm: use-cases/helm.md
   - Toolkit Components:
     - Overview: components/index.md