feature #931 Add support for creating a repo dispatch event (Nyholm)

This PR was squashed before being merged into the 2.x branch.

Discussion
----------

If you want to trigger a custom action, you need this API call. 

Commits
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6557c72 Add support for creating a repo dispatch evnet
a068d5c cs
a1527d5 Update URL
8a6a553 Style fix

Author: Nyholm

doc/repos.md

@@ -346,3 +346,11 @@ You can optionally assign some teams by passing an array with their ID's if you'
 ```php
 $repo = $client->api('repo')->transfer('KnpLabs', 'php-github-api', 'github', [1234]);
 ```
+
+### Create a repository dispatch event
+
+Example when you want to configure custom github action workflows.
+
+```php
+$client->api('repo')->dispatch('KnpLabs', 'php-github-api', 'acme-event', ['foo'=>'bar']);
+```

lib/Github/Api/Repo.php

@@ -276,6 +276,25 @@ public function readme($username, $repository, $format = 'raw')
         ]);
     }
 
+    /**
+     * Create a repository dispatch event.
+     *
+     * @link https://developer.github.com/v3/repos/#create-a-repository-dispatch-event
+     *
+     * @param string $username   the user who owns the repository
+     * @param string $repository the name of the repository
+     * @param string $eventType  A custom webhook event name
+     *
+     * @return mixed null on success, array on error with 'message'
+     */
+    public function dispatch($username, $repository, $eventType, array $clientPayload)
+    {
+        return $this->post(\sprintf('/repos/%s/%s/dispatches', rawurlencode($username), rawurlencode($repository)), [
+            'event_type' => $eventType,
+            'client_payload' => $clientPayload,
+        ]);
+    }
+
     /**
      * Manage the collaborators of a repository.
      *