Add documentation

docs/installation/kubernetes.en.md

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+[Documentation](../../README.md#documentation) → Installation → Kubernetes CSI
+
+-----
+
+[Читать на русском](kubernetes.ru.md)
+
+# Kubernetes CSI
+
+Vitastor has a CSI plugin for Kubernetes which supports RWO (and block RWX) volumes.
+
+To deploy it, take manifests from [csi/deploy/](../../csi/deploy/) directory, put your
+Vitastor configuration in [001-csi-config-map.yaml](../../csi/deploy/001-csi-config-map.yaml),
+configure storage class in [009-storage-class.yaml](../../csi/deploy/009-storage-class.yaml)
+and apply all `NNN-*.yaml` manifests to your Kubernetes installation:
+
+```
+for i in ./???-*.yaml; do kubectl apply -f $i; done
+```
+
+After that you'll be able to create PersistentVolumes. See example in [csi/deploy/example-pvc.yaml](../../csi/deploy/example-pvc.yaml).