Add Electrum ABC to supported wallets

Summary:
Temporary logo and link to releases until something more permanent is setup.

This change will not be landed until the next Electrum ABC release becomes available.

Test Plan: make serve

Reviewers: #bitcoin_abc, Mengerian

Reviewed By: #bitcoin_abc, Mengerian

Subscribers: Mengerian

Differential Revision: https://reviews.bitcoinabc.org/D8504