Fix typo in the Exposing your data in the Store API documentation (#43488)

* Fix basic usage code snippet example in extend-rest-api-add-data.md

* Add changefile(s) from automation for the following project(s): woocommerce-blocks

---------

Co-authored-by: github-actions <github-actions@github.com>

plugins/woocommerce-blocks/docs/third-party-developers/extensibility/rest-api/extend-rest-api-add-data.md

@@ -55,10 +55,10 @@ function my_schema_callback() {
 	return [
 		'custom-key' => [
 			'description' => __( 'My custom data', 'plugin-namespace' ),
-			'type' => 'string'
+			'type' => 'string',
 			'readonly' => true,
 		]
-	]
+	];
 }
 ```
 

plugins/woocommerce/changelog/43488-patch-1

@@ -0,0 +1,4 @@
+Significance: patch
+Type: dev
+
+This PR fixes a minor typo in the Exposing your data in the Store API doc.