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/AttrTransform/BoolToCSS.php

@@ -0,0 +1,36 @@
+<?php
+
+/**
+ * Pre-transform that changes converts a boolean attribute to fixed CSS
+ */
+class HTMLPurifier_AttrTransform_BoolToCSS extends HTMLPurifier_AttrTransform {
+
+    /**
+     * Name of boolean attribute that is trigger
+     */
+    protected $attr;
+
+    /**
+     * CSS declarations to add to style, needs trailing semicolon
+     */
+    protected $css;
+
+    /**
+     * @param $attr string attribute name to convert from
+     * @param $css string CSS declarations to add to style (needs semicolon)
+     */
+    public function __construct($attr, $css) {
+        $this->attr = $attr;
+        $this->css  = $css;
+    }
+
+    public function transform($attr, $config, $context) {
+        if (!isset($attr[$this->attr])) return $attr;
+        unset($attr[$this->attr]);
+        $this->prependCSS($attr, $this->css);
+        return $attr;
+    }
+
+}
+
+// vim: et sw=4 sts=4