Add safe_html() for XSS-safe WYSIWYG HTML sanitization

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

vendor/ezyang/htmlpurifier/library/HTMLPurifier/HTMLModule/XMLCommonAttributes.php

@@ -0,0 +1,20 @@
+<?php
+
+class HTMLPurifier_HTMLModule_XMLCommonAttributes extends HTMLPurifier_HTMLModule
+{
+    /**
+     * @type string
+     */
+    public $name = 'XMLCommonAttributes';
+
+    /**
+     * @type array
+     */
+    public $attr_collections = array(
+        'Lang' => array(
+            'xml:lang' => 'LanguageCode',
+        )
+    );
+}
+
+// vim: et sw=4 sts=4