Fix various compatibility issues with PHP 8

libs/ical/Property/RawStringValue.php

@@ -0,0 +1,20 @@
+<?php
+
+/*
+ * This file is part of the eluceo/iCal package.
+ *
+ * (c) Markus Poerschke <markus@eluceo.de>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+namespace Eluceo\iCal\Property;
+
+class RawStringValue extends StringValue
+{
+    public function getEscapedValue(): string
+    {
+        return $this->getValue();
+    }
+}