Add site banner, build number, and changelog

frontend/app/ui/HeaderActions.tsx

@@ -49,6 +49,7 @@ export default function HeaderActions() {
       <a className="header-cta header-cta--left" href="/feedback">Send feedback</a>
       <a href="/">Requests</a>
       <a href="/how-it-works">How it works</a>
+      <a href="/changelog">Changelog</a>
       <a href="/profile">My profile</a>
       {role === 'admin' && <a href="/admin">Settings</a>}
       <button type="button" className="header-link" onClick={signOut}>