refactor: add phpstan and update code to adhere to level 5

- move and refactor Image.php from Libraries to Entities folder
- update some database field names
/ types
- update composer packages

app/Controllers/PlatformController.php

@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * @copyright  2020 Podlibre
+ * @license    https://www.gnu.org/licenses/agpl-3.0.en.html AGPL3
+ * @link       https://castopod.org/
+ */
+
+namespace App\Controllers;
+
+use CodeIgniter\HTTP\ResponseInterface;
+use App\Models\PlatformModel;
+use CodeIgniter\Controller;
+
+/*
+ * Provide public access to all platforms so that they can be exported
+ */
+class PlatformController extends Controller
+{
+    public function index(): ResponseInterface
+    {
+        $model = new PlatformModel();
+
+        return $this->response->setJSON($model->getPlatforms());
+    }
+}