docs: add helm values declarative syntax (argoproj#13661)

The Helm section of the user guide is missing an example of using `source.helm.values`.

Signed-off-by: Nicholas Morey <nicholas@morey.tech>

docs/user-guide/helm.md

@@ -50,6 +50,29 @@ source:
     - values-production.yaml
 ```
 
+## Values
+
+Argo CD supports the equivalent of a values file directly in the Application manifest using the `source.helm.values` key.
+
+```
+source:
+  helm:
+    values: |
+      ingress:
+        enabled: true
+        path: /
+        hosts:
+          - mydomain.example.com
+        annotations:
+          kubernetes.io/ingress.class: nginx
+          kubernetes.io/tls-acme: "true"
+        labels: {}
+        tls:
+          - secretName: mydomain-tls
+            hosts:
+              - mydomain.example.com
+```
+
 ## Helm Parameters
 
 Helm has the ability to set parameter values, which override any values in