Fix: render <blockquote> better on mobile
As mentioned in #707 (closed), the rendering of <blockquote>s didn't quite work
on smaller devices, as they were either not rendering for the full width
of the page (as each <p> was max-width'd themselves) or would be
indented too far, reducing the screen width.
This ensures that the <p>s within the <blockquote> fits nicely and
uses space on mobile more carefully.
Closes #707 (closed).