Fix wrong styling of todo items in exported HTML

The issue happened because styles connected with todo list were applied directly to HTML in Preview component. I added class to `li` tag of each todo item and style it from css.

browser/lib/utils.js

@@ -0,0 +1,11 @@
+export function lastFindInArray (array, callback) {
+  for (let i = array.length - 1; i >= 0; --i) {
+    if (callback(array[i], i, array)) {
+      return array[i]
+    }
+  }
+}
+
+export default {
+  lastFindInArray
+}