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

tests/session/ExampleSessionTest.php

@@ -0,0 +1,18 @@
+<?php
+
+class ExampleSessionTest extends \Tests\Support\SessionTestCase
+{
+	public function setUp(): void
+	{
+		parent::setUp();
+	}
+
+	public function testSessionSimple()
+	{
+		$this->session->set('logged_in', 123);
+
+		$value = $this->session->get('logged_in');
+
+		$this->assertEquals(123, $value);
+	}
+}