[e.cash] Place common sections

Summary:
Placing some common sections where they go

• tech page
• about page
• build page

Mistakely placed some sections before on the build page that arent
in the mockup so removing those

Test Plan: preview and check

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D18476