[e.cash] Recently built section

Summary:
Adding the recently built section to /tech page
features 8 prominent projects and a scrolling animation

• added the /build redirect to the preview config to get build page working with the preview bot since it uses a link to it here

Test Plan: preview and check it out

Reviewers: #bitcoin_abc, bytesofman, Klakurka

Reviewed By: #bitcoin_abc, bytesofman, Klakurka

Subscribers: Klakurka, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D18443