docs: Add documentation about running on Openshift.

Signed-off-by: John Allberg <john@ayoy.se>

docs/docs/installation/configuration/Openshift.md

@@ -0,0 +1,23 @@
+---
+comments: true
+---
+
+# Installing on Openshift
+
+To install on Openshift, set the value `global.isOpenshift` in the `values.yaml` file to true.
+In practice this means that `runAsUser` and `runAsGroup` are removed, since
+Openshift sets those automatically.
+
+You can set the `global.isOpenshift` parameter when running the `helm install` command:
+
+```shell
+helm install keptn keptn --set global.openShift.enabled=true
+```
+
+or you can define it in your `values.yaml` file:
+
+```yaml
+global:
+  openShift:
+    enabled: true
+```

mkdocs.yml

@@ -125,6 +125,7 @@ nav:
               - vCluster installation: docs/installation/configuration/vcluster.md
               - Keptn + cert-manager.io: docs/installation/configuration/cert-manager.md
               - Deploy Keptn via ArgoCD: docs/installation/configuration/argocd.md
+              - Deploy Keptn on OpenShift: docs/installation/configuration/Openshift.md
           - Installation Tips and Tricks: docs/installation/tips-tricks.md
           - Troubleshooting Guide: docs/installation/troubleshooting.md
           - Kubernetes cluster: docs/installation/k8s.md