Add troubleshooting doc

TROUBLESHOOTING.md

@@ -0,0 +1,31 @@
+# Troubleshooting
+
+### Turn on verbose mode
+
+```php
+$curl = new Curl();
+$curl->verbose();
+```
+
+### Compare output with and without the library
+
+```php
+$curl = new Curl();
+$curl->get('https://www.example.com/');
+var_dump($curl);
+```
+
+```php
+$ch = curl_init();
+curl_setopt($ch, CURLINFO_HEADER_OUT, true);
+curl_setopt($ch, CURLOPT_HEADER, false);
+curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+curl_setopt($ch, CURLOPT_URL, 'https://www.example.com/');
+curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'GET');
+curl_setopt($ch, CURLOPT_HTTPGET, true);
+$raw_response = curl_exec($ch);
+$curl_error_code = curl_errno($ch);
+$curl_error_message = curl_error($ch);
+$http_status_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
+$request_headers = curl_getinfo($ch, CURLINFO_HEADER_OUT);
+```