[e.cash] Fix footer issues

Summary:
Footer needs some width adjusment on medium screens
-moved blog link under about to avoid single item column
-added large breakpoint to theme
-modify css to accomodate footer on medium screens

Test Plan: preview the site and check the footer looks good and doesnt cause horizontal overflow

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D14232