Add command to list locales used in a project

This way we can more easily download all locales in a cli script (fetch
them using this command and then download in a loop)

bin/onesky

@@ -17,4 +17,5 @@ $application->add(new Teamleader\OneSky\InitCommand());
 $application->add(new Teamleader\OneSky\UploadCommand());
 $application->add(new Teamleader\OneSky\DownloadCommand());
 $application->add(new Teamleader\OneSky\MergeCommand());
+$application->add(new Teamleader\OneSky\ListLocaleCommand());
 $application->run();

src/ListLocaleCommand.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Teamleader\OneSky;
+
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class ListLocaleCommand extends Command
+{
+    protected function configure()
+    {
+        parent::configure();
+        $this
+            ->setName('list-locale')
+            ->setDescription('List the locale enabled in the project');
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        $this->initializeClient($input->getOption('key'), $input->getOption('secret'));
+
+        $project_id = $input->getOption('project_id');
+        if (is_null($project_id)) {
+            $project_id = $this->config['project_id'];
+        }
+
+        $response = $this->client->projects('languages', [
+            'project_id' => $project_id,
+        ]);
+
+        if (!$response) {
+            $output->writeln('<error>Empty OneSky response!</error>');
+            exit(1);
+        }
+
+        $data = json_decode($response, true);
+        if (isset($data['meta']) && $data['meta']['status'] != 200) {
+            $output->writeln('<error>' . $data['meta']['message'] . '</error>');
+            exit(1);
+        }
+
+        foreach ($data['data'] as $language) {
+            $output->writeln($language['code']);
+        }
+    }
+}