Adds docs and example for webhook

asana.php

@@ -1141,6 +1141,8 @@ public function removeCustomFieldFromProject($projectId, $customFieldId)
 
     /**
      * Creates a webhook.
+     * Please read the documentation (or see webhook-target.php inside examples) as the target must be a valid url and must return a valid header back.
+     * https://asana.com/developers/api-reference/webhooks
      *
      * @param string $resourceId A resource ID to subscribe to. The resource can be a task or project.
      * @param string $target The URL to receive the HTTP POST.

examples/webhook-target.php

@@ -0,0 +1,11 @@
+<?php
+/**
+ * This is just a simple example of a webhook target that you must implement in order to be able to create it properly with the API.
+ * The url should respond to https POST requests and has to be accessible by ASANA.
+ *
+ * For more information please read the following resources:
+ * https://asana.com/developers/api-reference/webhooks
+ * http://resthooks.org/docs/security/
+ */
+header('x-hook-secret: ' . $_SERVER['HTTP_X_HOOK_SECRET']);
+echo '200 OK';