docs: generic.css: Indentation and spacing tweaks

docs: generic.css: Indentation and spacing tweaks

- Add line-height:150% spacing for all text. This makes text lines far
  less cramped, and seems closer visually to what wikipedia uses.

- Remove bottom and top margin from lists: entries seemed needlessly
  spread out.

- Reduce sublist indentation a bit

- Add a bottom border after headings: IMO this greatly helps in break
  up the vertical flow of a big page of text. Doesn't look great on the
  front page, but helps a lot on dense pages like formatdomain