[add] HTML Purifier added to clean code

inc/3rdparty/htmlpurifier/HTMLPurifier/ConfigSchema/schema/Attr.AllowedClasses.txt

@@ -0,0 +1,8 @@
+Attr.AllowedClasses
+TYPE: lookup/null
+VERSION: 4.0.0
+DEFAULT: null
+--DESCRIPTION--
+List of allowed class values in the class attribute. By default, this is null,
+which means all classes are allowed.
+--# vim: et sw=4 sts=4