postAjax function
Sends an Ajax request to the given url
using the POST method.
Implementation
Future<List<int>?> postAjax(Uri url, {
List<int>? data, String? body, Map<String, String>? headers,
bool? onResponse(HttpClientResponse response)?})
=> ajax(url, method: "POST", data: data, body: body,
headers: headers, onResponse: onResponse);