[e.cash] Move Technology menu items to Build page

Summary: Reduce the top menu by one item, and move the technical info to a more relevant place

Test Plan: Run it locally, check that it looks good and links work

Reviewers: #bitcoin_abc, johnkuney, bytesofman

Reviewed By: #bitcoin_abc, johnkuney, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D16891