[e.cash] Add footer to layout

Summary: Adding the footer to the layout component. It uses the same link data for the navbar to render footer links, along with social links and contact email

Test Plan:
@bot preview-e.cash
-scroll to bottom of the page to view the footer
-check everything looks good on mobile and both themes
-check links work

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D13908