Improved article typography

The typography for the site looks great, but I think fonts for technical documentation articles should, above all else, be as readable as possible.

Currently, article fonts are eye-catching with slightly low contrast, a slightly large size, a light weight, and high line spacing. This commit makes article typography completely boring and readable: normal contrast, normal size, normal weight, and normal line spacing.

It also renders emphasized text as italicized text. Using underlined text for emphasized text makes them look like links.

IMHO :)