feat: add npm for js dependencies + move src/ files to root folder

- add node service in docker-compose.yml
- update .devcontainer Dockerfile by adding node, npm and vim
- init package.json for npm with tailwindcss, postcss, commitlint and commitizen as dev dependencies
- update default layout main header and footer
- replace CI's welcome_message.php with home.php listing all podcasts
- add AUTHORS.md file
- add docs folder in which to place castopod's technical documentation

app/Models/LanguageModel.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class LanguageModel extends Model
+{
+    protected $table = 'languages';
+    protected $primaryKey = 'id';
+
+    protected $allowedFields = [
+        'code', 'native_name'
+    ];
+
+    protected $returnType = 'App\Entities\Language';
+    protected $useSoftDeletes = false;
+
+    protected $useTimestamps = false;
+}