feat(request): add timeout configuration

[usernane]

Problem

Cannot configure request timeouts.

Suggestion

Add timeout option to configuration and setTimeout() method.

Example API

const ajax = new AJAXRequest({
  url: '/api/data',
  timeout: 5000, // 5 seconds
  onTimeout: function() {
    console.log('Request timed out');
  }
});

// Or via method
ajax.setTimeout(5000);