refactor: add php_codesniffer to define castopod's coding style based on psr-1

- add .editorconfig file
- format all files to comply with castopod's coding style
- switch parsedown dependency with commonmark library to better follow commonmark spec for markdown
- add prettier command to format all project files at once

closes #16

app/Controllers/BaseController.php

@@ -50,8 +50,8 @@ class BaseController extends Controller
         set_user_session_referer();
     }
 
-    protected static function triggerWebpageHit($postcast_id)
+    protected static function triggerWebpageHit($podcastId)
     {
-        webpage_hit($postcast_id);
+        webpage_hit($podcastId);
     }
 }