[e.cash] Add hand image to hero section

Summary: Adding the background hand image to the top section

Test Plan:
@bot preview-e.cash
See if the hand image is there and looks good
Check both themes

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D13855