[fix] skip HTML + PHP mix in DeclareStrictTypesTestsRector to avoid mallformed code

Author: TomasVotruba

rules-tests/CodeQuality/Rector/StmtsAwareInterface/DeclareStrictTypesTestsRector/Fixture/skip_html_php_mix.php.inc

@@ -0,0 +1,12 @@
+<img src="asdf">
+
+<?php
+
+use PHPUnit\Framework\TestCase;
+
+final class SkipHtmlPHPMix extends TestCase
+{
+    public function test()
+    {
+    }
+}

rules/CodeQuality/Rector/StmtsAwareInterface/DeclareStrictTypesTestsRector.php

@@ -74,6 +74,10 @@ public function beforeTraverse(array $nodes): ?array
     {
         parent::beforeTraverse($nodes);
 
+        if ($this->file->containsHTML()) {
+            return null;
+        }
+
         if ($this->shouldSkipNodes($nodes, $this->file)) {
             return null;
         }