[SPARK-53722] Document workloadResources.sparkApplicationSentinel.name

### What changes were proposed in this pull request?

This PR aims to document `workloadResources.sparkApplicationSentinel.name`.

### Why are the changes needed?

https://github.com/apache/spark-kubernetes-operator/blob/aacb7a47ee3e60c41615e5db85865c6d06992d18/build-tools/helm/spark-kubernetes-operator/values.yaml#L154

### Does this PR introduce _any_ user-facing change?

No behavior change.

### How was this patch tested?

Manual review because this is a doc change.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes apache#348 from dongjoon-hyun/SPARK-53722.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

docs/operations.md

@@ -112,6 +112,7 @@ following table:
 | workloadResources.labels                                         | Labels to be applied for all workload resources.                                                                                                                               | `"app.kubernetes.io/component": "spark-workload"`                                                       |
 | workloadResources.annotations                                    | Annotations to be applied for all workload resources.                                                                                                                          | `"helm.sh/resource-policy": keep`                                                                       |
 | workloadResources.sparkApplicationSentinel.create                | If enabled, sentinel resources will be created for operator to watch and reconcile for the health probe purpose.                                                               | false                                                                                                   |
+| workloadResources.sparkApplicationSentinel.name                  | Name for sentinel resources.                                                                                                                                                   | "spark-app-sentinel"                                                                                    |
 | workloadResources.sparkApplicationSentinel.sentinelNamespaces    | A list of namespaces where sentinel resources will be created in. Note that these namespaces have to be a subset of `workloadResources.namespaces.data`.                       |                                                                                                         |
 | operatorConfiguration.append                                     | If set to true, below conf file & properties would be appended to default conf. Otherwise, they would override default properties.                                             | true                                                                                                    |
 | operatorConfiguration.log4j2.properties                          | The default log4j2 configuration.                                                                                                                                              | Refer default [log4j2.properties](../build-tools/helm/spark-kubernetes-operator/conf/log4j2.properties) |