Add example for docs

Author: marccampbell

examples/preflight/check-kubernetes-version.yaml

@@ -0,0 +1,18 @@
+apiVersion: troubleshoot.replicated.com/v1beta1
+kind: Preflight
+metadata:
+  name: check-kubernetes-version
+spec:
+  analyzers:
+    - clusterVersion:
+        outcomes:
+          - fail:
+              when: "< 1.14.0"
+              message: The application requires at Kubernetes 1.14.0 or later, and recommends 1.15.0.
+              uri: https://www.kubernetes.io
+          - warn:
+              when: "< 1.15.0"
+              message: Your cluster meets the minimum version of Kubernetes, but we recommend you update to 1.15.0 or later.
+              uri: https://kubernetes.io
+          - pass:
+              message: Your cluster meets the recommended and required versions of Kubernetes.