added isReadOnly Reflection method https://youtrack.jetbrains.com/issue/WI-67662

Author: DmitryTronin

Reflection/ReflectionClass.php

@@ -425,6 +425,13 @@ public function isAbstract(): bool {}
     #[TentativeType]
     public function isFinal(): bool {}
 
+    /**
+     * @return bool
+     */
+    #[Pure]
+    public function isReadOnly(): bool {}
+
+
     /**
      * Gets modifiers
      *