refactor: add rector to enforce type declarations, code quality + style and remove dead code

- update CI process to include quality stage (tests + code review)
- add captainhook to install git pre-commit & pre-push hooks
- remove .devcontainer Dockerfile to use project's docker-compose services: all
services can now be started automatically using vscode
- update docs/setup-development.md

tests/session/ExampleSessionTest.php

@@ -1,13 +1,16 @@
 <?php
 
-class ExampleSessionTest extends \Tests\Support\SessionTestCase
+namespace Tests\Session;
+
+use Tests\Support\SessionTestCase;
+class ExampleSessionTest extends SessionTestCase
 {
     public function setUp(): void
     {
         parent::setUp();
     }
 
-    public function testSessionSimple()
+    public function testSessionSimple(): void
     {
         $this->session->set('logged_in', 123);