[e.cash] Add mining page

Summary:
Adding the mining page. We dont have a design mockup for this one
so basically just taking all the content from the current page and
implementing here

Test Plan: preview and check, review content

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D18492