[e.cash] Add social card image

Summary:
Adding the social card image. The tag is already there, just needs to
point to this image. Will only be testable live as social image urls still have to
be absolute urls

Test Plan: Check the social image url in layout.tsx points to this image. Any image suggestions

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D18531