Add website to client repository

Closes #1567

The main reason I'm not simply merging Annika's PR is because this
way makes it clearer that I'm taking responsibility for all this
code, that it's mostly code I wrote, and also because it makes it
easier to ensure that none of the files have been changed.

(Not that I don't personally trust Annika, but I have something
resembling an obligation to users not to expose them to risks based
on personal trust.)

website/lib/htmlpurifier/HTMLPurifier/HTMLModule/Tidy/Strict.php

@@ -0,0 +1,21 @@
+<?php
+
+class HTMLPurifier_HTMLModule_Tidy_Strict extends HTMLPurifier_HTMLModule_Tidy_XHTMLAndHTML4
+{
+    public $name = 'Tidy_Strict';
+    public $defaultLevel = 'light';
+
+    public function makeFixes() {
+        $r = parent::makeFixes();
+        $r['blockquote#content_model_type'] = 'strictblockquote';
+        return $r;
+    }
+
+    public $defines_child_def = true;
+    public function getChildDef($def) {
+        if ($def->content_model_type != 'strictblockquote') return parent::getChildDef($def);
+        return new HTMLPurifier_ChildDef_StrictBlockquote($def->content_model);
+    }
+}
+
+// vim: et sw=4 sts=4