Replace PayPal buttons with DuckDuckGo challenge

wiki/src/donate.css

@@ -137,6 +137,19 @@ span.title {
 }
 
 #duckduckgo {
+  background: #b49cd3;
+  padding: 2em;
+}
+
+#duckduckgo a {
+  color: #333;
+  font-weight: bold;
+  border-color: black;
+  background-image: none;
+  padding-right: 0 !important;
+}
+
+#paypal {
   margin-bottom: 3em;
 }