style: Adopt PSR12

Dev dependency flyeralarm/php-code-validator has been removed.

Closes #444

Behavioral/NullObject/Logger.php

@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\NullObject;
 

Behavioral/NullObject/NullLogger.php

@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\NullObject;
 

Behavioral/NullObject/PrintLogger.php

@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\NullObject;
 

Behavioral/NullObject/Service.php

@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\NullObject;
 
@@ -14,6 +16,6 @@ class Service
     public function doSomething()
     {
         // notice here that you don't have to check if the logger is set with eg. is_null(), instead just use it
-        $this->logger->log('We are in '.__METHOD__);
+        $this->logger->log('We are in ' . __METHOD__);
     }
 }

Behavioral/NullObject/Tests/LoggerTest.php

@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\NullObject\Tests;