docs: add helm section on patching resources

docs/content/examples/helm/_index.md

@@ -1,4 +1,4 @@
-To define a helm release, use the {{< option "kubernetes.helm.releases" >}} option.
+To define a Helm release, use the {{< option "kubernetes.helm.releases" >}} option.
 
 {{< source "default.nix" >}}
 
@@ -7,3 +7,25 @@ Fetch and render the chart just as we did with plain manifests:
 ```sh
 nix eval -f . --json config.kubernetes.generated
 ```
+
+## patching
+
+A common issue with Helm charts is the need to template everything under the sun.
+Kubenix solves this issue by merging configuration during evaluation.
+
+For example, to patch the deployment created by the release above:
+
+```nix
+{
+  # define a resource with the same name
+  kubernetes.resources.deployments.nginx = {
+    # be sure to match the corresponding namespace as well
+    metadata.namespace = "default";
+    # here we can configure anything and are no longer bound by `values.yaml` 
+    spec.template.spec.containers.nginx.env = [{
+      name = "MY_VARIABLE";
+      value = "100";
+    }];
+  };
+}
+```