fix(elasticsearch-plugin): Close down es client when app closes

packages/elasticsearch-plugin/src/plugin.ts

@@ -132,6 +132,11 @@ export class ElasticsearchPlugin implements VendurePlugin {
         });
     }
 
+    /** @internal */
+    onClose() {
+        return this.client.close();
+    }
+
     /** @internal */
     extendAdminAPI(): APIExtensionDefinition {
         return {