[e.cash] add mkpool to e.cash/mining page

Summary: Added mkpool to e.cash/mining in the solo mining section.

Test Plan: load e.cash/mining and check the link. 'mkpool' in small caps is intended.

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D20344