add usage

Signed-off-by: Chip Zoller <[email protected]>

README.md

@@ -5,3 +5,33 @@ This repo is for an **experimental only** demo application which shows how Kyver
 ## Installation
 
 See installation instructions in the Helm chart's README [here](/charts/kyverno-json-validator/README.md#installing-the-chart).
+
+## Usage
+
+The chart will install the CRD which maps onto a generic JSON payload with pseudo-Kubernetes Custom Resource called `MyJson`. Install a matching Kyverno policy which contains the validation you wish to make.
+
+```yaml
+apiVersion: kyverno.io/v1
+kind: ClusterPolicy
+metadata:
+  name: json-test
+spec:
+  background: false
+  validationFailureAction: Enforce
+  rules:
+  - name: test
+    match:
+      any:
+      - resources:
+          kinds:
+          - MyJson
+    validate:
+      message: The value of `foo` must be set to `bar`.
+      pattern:
+        spec:
+          foo: bar
+```
+
+Navigate to the UI using the link provided after the chart was installed (which varies depending on whether you used the default of ClusterIP or LoadBalancer) and validate the JSON payload you wish. Validation failures return the message from Kyverno defined in the `message` field of the matching policy.
+
+![gif](static/gif.gif)