WIP: Bug 1038395 - Build CTA landing page for learners / makers

<http://localhost:9006/from/firefox-2014/>
<http://localhost:9006/for/learners/>
<http://localhost:9006/for/mentors/>
Is there technically a chance that `sessionStorage.setItem()` could throw if e.g. the user is in private browsing mode or storage is full? I know that was the case a few years ago with `localStorage`, but not sure if it applies here.