Until per-domains stylesheets are implemented, there is no way to
apply style to the readability page only. With this patch, you can
just use the global setting `content.user_stylesheets` by writing
a more specific CSS selector. For example:
body.qute-readability {
font-family: Libertinus;
font-size: 1.2em;
text-align: justify;
}
will change the font and text alignment of the readability page,
without altering the style of other websites.
Closes#4951. Produces dynamically resizable page margins and
increases line heights in order to enhance readability (based on
'desgin principles' from http://bettermotherfuckingwebsite.com/)