Add REST API request example header (#48627)

Author: gracepark

Diff for: data/ui.yml

@@ -139,6 +139,8 @@ rest_reference:
   notes: Notes
   parameters: Parameters for "{{ RESTOperationTitle }}"
   response: Response
+  request_example: Request example
+  request_examples: Request examples
   example_response: Example response
   status_code: Status code
   http_status_code: HTTP response status codes for "{{ RESTOperationTitle }}"

Diff for: src/fixtures/fixtures/data/ui.yml

@@ -139,6 +139,8 @@ rest_reference:
   notes: Notes
   parameters: Parameters for "{{ RESTOperationTitle }}"
   response: Response
+  request_example: Request example
+  request_examples: Request examples
   example_response: Example response
   status_code: Status code
   http_status_code: HTTP response status codes for "{{ RESTOperationTitle }}"

Diff for: src/rest/components/RestCodeSamples.tsx

@@ -224,7 +224,9 @@ export function RestCodeSamples({ operation, slug, heading }: Props) {
       <h3 className="mt-0 pt-0 h4" id={`${slug}--code-samples`}>
         <a href={`#${slug}--code-samples`}>{heading}</a>
       </h3>
-
+      <h4 className="mt-3 mb-3 h5">
+        {isSingleExample ? t('request_example') : t('request_examples')}
+      </h4>
       {/* Display an example selector if more than one example */}
       {!isSingleExample && (
         <div className="pb-5 pt-2">