Add documentation for --api-versions flag in template command

The --api-versions flag was undocumented in the template command's
help text. This adds usage documentation and examples showing both
comma-separated and multiple flag usage patterns.

Fixes #13198

Signed-off-by: majiayu000 <1835304752@qq.com>

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: majiayu000 <1835304752@qq.com>

pkg/cmd/template.go

@@ -46,6 +46,16 @@ Render chart templates locally and display the output.
 Any values that would normally be looked up or retrieved in-cluster will be
 faked locally. Additionally, none of the server-side testing of chart validity
 (e.g. whether an API is supported) is done.
+
+To specify the Kubernetes API versions used for Capabilities.APIVersions, use
+the '--api-versions' flag. This flag can be specified multiple times or as a
+comma-separated list:
+
+    $ helm template --api-versions networking.k8s.io/v1 --api-versions cert-manager.io/v1 mychart ./mychart
+
+or
+
+    $ helm template --api-versions networking.k8s.io/v1,cert-manager.io/v1 mychart ./mychart
 `
 
 func newTemplateCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {