[e.cash] Add Swapspace widget

Summary: Adding the Swapspace widget next to the Swapzone widget on /get-ecash as requested

Test Plan: Preview the site and check the widget

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D17439