Document the proxy endpoint

Signed-off-by: Jamie Klassen <jklassen@vmware.com>

plugins/kubernetes-backend/api-report.md

@@ -141,7 +141,7 @@ export class GoogleServiceAccountAuthTranslator
   ): Promise<GKEClusterDetails>;
 }
 
-// @alpha
+// @public
 export const HEADER_KUBERNETES_CLUSTER: string;
 
 // @alpha (undocumented)

plugins/kubernetes-backend/src/service/KubernetesProxy.ts

@@ -32,7 +32,7 @@ export const APPLICATION_JSON: string = 'application/json';
 /**
  * The header that is used to specify the cluster name.
  *
- * @alpha
+ * @public
  */
 export const HEADER_KUBERNETES_CLUSTER: string = 'X-Kubernetes-Cluster';