[e.cash] Blog style edits

Summary:
Proposed edits to improve blog layout

• Use larger version of images for better quality
• Remove the "read more" buttons as the whole card is clickable and they are repetitive noise
• reduce max width of page on desktop for better readability

Test Plan: preview and compare /blog and post pages with live site

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D18766