[e.cash] Landing page design updates

Summary: Refreshing the landing page content and design to provide better calls to action and messaging

Test Plan: preview the site and see if landing page looks good

Reviewers: #bitcoin_abc, Mengerian

Reviewed By: #bitcoin_abc, Mengerian

Subscribers: Kronkmeister, Klakurka, Mengerian, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D16556