add forbidden option test

Author: devnexen

ext/tidy/tests/tidy_error1.phpt

@@ -20,11 +20,20 @@ try {
 $config = ['neither'];
 try {
 	$tidy->parseString($buffer, $config);
-} catch (\Error $e) {
+} catch (\TypeError $e) {
+	echo $e->getMessage(), PHP_EOL;
+}
+
+$config = ['doctype-mode' => 'customtag'];
+
+try {
+	var_dump($tidy->parseString($buffer, $config));
+} catch (\ValueError $e) {
 	echo $e->getMessage(), PHP_EOL;
 }
 
 ?>
---EXPECTF--
+--EXPECT--
 tidy::parseString(): Argument #2 ($config) Unknown Tidy configuration option "bogus"
 tidy::parseString(): Argument #2 ($config) must be of type array with keys as string
+tidy::parseString(): Argument #2 ($config) Attempting to set read-only option "doctype-mode"