Test: skip include plugin on PHP < 8

Author: annda

_test/OutputTest.php

@@ -77,6 +77,10 @@ public function test_output()
 
     public function test_include_missing_output()
     {
+        if (PHP_MAJOR_VERSION < 8) {
+            $this->markTestSkipped("Include plugin requires PHP >= 8, skipping test.");
+        }
+
         global $ID;
         $page = 'page01';
         $includedPage = 'foo';