Document missing template field

Templates work for manifests, too.
So document `setValueTemplates` since we are actually using it.

docs-v2/content/en/docs/environment/templating.md

@@ -35,6 +35,7 @@ will be `gcr.io/k8s-skaffold/example:v1`.
 * `deploy.kubectl.defaultNamespace`
 * `deploy.kustomize.defaultNamespace`
 * `manifests.kustomize.paths.[]`
+* `manifests.helm.releases[].setValueTemplates`
 * `portForward.namespace`
 * `portForward.resourceName`
 
@@ -65,4 +66,4 @@ The templating pipelines provided by Go templates can be quite comprehensive whe
   ```default now .SOURCE_DATE_EPOCH | date "2006-01-02T15:04:05-0700"``` 
 * The idiomatic seven-character abbreviated Git hash is easily accessible:
 
-  ```cmd "bash" "-c" "git rev-parse HEAD" | substr 0 7```
+  ```cmd "bash" "-c" "git rev-parse HEAD" | substr 0 7```