Add simple Kubernetes example

examples/kubernetes-simple/README.md

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+# PlantUML Kubernetes Deployment
+
+In this example, PlantUML is deployed on an Kubernetes cluster using a `Deployment`, a `Service` and an `Ingress`.
+
+## Quick start
+
+Install:
+
+```bash
+# Hint: Adjust the Ingress host to your URL
+
+kubectl create ns plantuml
+kubectl -n plantuml apply -f deployment.yaml
+```
+
+Uninstall:
+
+```bash
+kubectl -n plantuml delete -f deployment.yaml
+kubectl delete ns plantuml
+```
+
+## TLS configuration
+
+Create a TLS `Secret` and extend the `Ingress` spec with a TLS configuration:
+
+```bash
+[...]
+  tls:
+  - hosts:
+    - plantuml-example.localhost
+    secretName: plantuml-tls
+```
+
+Since the `Ingress Controller` terminates the TLS and routes `http` to the application, we might need to tell the application explicitly that it got a forwarded request.
+
+This configuration changes depending on the `Ingress Controller`. Here an nginx example:
+
+```
+annotations:
+  kubernetes.io/ingress.class: nginx
+  nginx.ingress.kubernetes.io/configuration-snippet: |
+    more_set_headers "X-Forwarded-Proto: https";
+```
+
+## Useful commands
+
+```bash
+# see whats going on inside your Deployment
+kubectl -n plantuml logs -l "app.kubernetes.io/name=plantuml"
+```