chore: setup PHPStan for project tooling

(cherry picked from commit 71e30a0a)

Co-authored-by: Jan Wennrich <jan.wennrich@pcsg.de>

.gitignore

 
 tools/
+
+phpstan.neon

.phive/phars.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<phive xmlns="https://phar.io/phive">
+  <phar name="phpstan" version="1.11.1" installed="1.11.1" location="./tools/phpstan" copy="false"/>
+</phive>

phpstan.dist.neon

+includes:
+	- phpstan-baseline.neon
+
+parameters:
+    level: 8
+    paths:
+        - src
+        - ajax
+    tipsOfTheDay: false

tests/phpstan-bootstrap.php

+<?php
+
+if (!defined('QUIQQER_SYSTEM')) {
+    define('QUIQQER_SYSTEM', true);
+}
+
+if (!defined('QUIQQER_AJAX')) {
+    define('QUIQQER_AJAX', true);
+}
+
+putenv("QUIQQER_OTHER_AUTOLOADERS=KEEP");
+
+require_once __DIR__ . '/../../../../bootstrap.php';