Docs: Add system version with format yaml

Signed-off-by: ChengHao Yang <17496418+tico88612@users.noreply.github.com>

Author: tico88612

docs/command-reference.md

@@ -1033,7 +1033,7 @@ container system version [--format <format>]
 
 **Options**
 
-*   `--format <format>`: Output format (values: json, table; default: table)
+*   `--format <format>`: Output format (values: json, table, yaml; default: table)
 
 **Table Output**
 
@@ -1070,6 +1070,21 @@ Backward-compatible with previous CLI-only output. Top-level fields describe the
 }
 ```
 
+**YAML Output**
+
+Equivalent to the JSON output but in YAML format. Each entry in the array represents a component.
+
+```yaml
+- version: 1.2.3
+  buildType: debug
+  commit: abcdef1
+  appName: container
+- version: 1.2.3
+  buildType: release
+  commit: 1234abc
+  appName: container-apiserver
+```
+
 ### `container system logs`
 
 Displays logs from the container services. You can specify a time interval or follow new logs in real time.