Revert "remove htmlpurifier"

This reverts commit c21a462d52.

lib/htmlpurifier/library/HTMLPurifier/ConfigSchema/schema/AutoFormat.PurifierLinkify.DocURL.txt

@@ -0,0 +1,12 @@
+AutoFormat.PurifierLinkify.DocURL
+TYPE: string
+VERSION: 2.0.1
+DEFAULT: '#%s'
+ALIASES: AutoFormatParam.PurifierLinkifyDocURL
+--DESCRIPTION--
+<p>
+  Location of configuration documentation to link to, let %s substitute
+  into the configuration's namespace and directive names sans the percent
+  sign.
+</p>
+--# vim: et sw=4 sts=4