Rip off CSS from Firefox's reading mode

[mcatanzaro]

In Firefox, navigate to chrome://global/skin/aboutReaderContent.css

Wow, look at that, a nice GPL-compatible stylesheet that is very close to what GNOME News is trying to do! I recommend stealing as much of this as is reasonable, since they are kind enough to use a free license. Some notable differences between Firefox and GNOME News:

• Firefox has larger line spacing throughout, which makes content easier to read.
• Firefox has more vertical space between many elements (notably list items).
• Firefox has heuristics to hide certain page content.

For #76 I picked a few items from this stylesheet to fix only the problem I was trying to solve, but ignored the rest of it.

[allanday]

The layout of the Firefox Reader Mode is nice.