feat(episodes): add create form and view pages for episode

- add james-heinrich/getid3 library as a dependency to composer.json
- update DEPENDENCIES.md file
- fix episodes table migration script
- add js devDependencies: prettier, @prettier/plugin-php and lint-staged to automatically format staged files before commit
- reformat all files to the prettier format
- refactor code by separating some logic as helper functions
- overwrite existing files when uploading new files with the same name

fixes #1

app/Models/EpisodeModel.php

@@ -1,4 +1,9 @@
 <?php
+/**
+ * @copyright  2020 Podlibre
+ * @license    https://www.gnu.org/licenses/agpl-3.0.en.html AGPL3
+ * @link       https://castopod.org/
+ */
 
 namespace App\Models;
 
@@ -10,8 +15,9 @@ class EpisodeModel extends Model
     protected $primaryKey = 'id';
 
     protected $allowedFields = [
-        'slug',
+        'podcast_id',
         'title',
+        'slug',
         'enclosure_url',
         'enclosure_length',
         'enclosure_type',