Add documentation about pagination of the API (#20740)

* Add documentation about pagination of the API

* Update docs/content/doc/developers/api-usage.en-us.md

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

docs/content/doc/developers/api-usage.en-us.md

@@ -105,6 +105,18 @@ curl -X POST "http://localhost:4000/api/v1/repos/test1/test1/issues" \
 As mentioned above, the token used is the same one you would use in
 the `token=` string in a GET request.
 
+## Pagination
+
+The API supports pagination. The `page` and `limit` parameters are used to specify the page number and the number of items per page. As well, the `Link` header is returned with the next, previous, and last page links if there are more than one pages. The `x-total-count` is also returned to indicate the total number of items.
+
+```sh
+curl -v "http://localhost/api/v1/repos/search?limit=1"
+...
+< link: <http://localhost/api/v1/repos/search?limit=1&page=2>; rel="next",<http://localhost/api/v1/repos/search?limit=1&page=5252>; rel="last"
+...
+< x-total-count: 5252
+```
+
 ## API Guide:
 
 API Reference guide is auto-generated by swagger and available on: