Add a CSS reset to the docs

[mahkoh]

Both the text and the background are black in the steam ingame browser.

[thestinger]

The Steam in-game browser is still on Chromium 35 (known security bugs and all) so I think this is more a problem on their end.

[tomjakubowski]

We probably just need to set background-color to a light color ourselves. It wouldn't surprise me if Steam has a user agent style that sets the default background color to dark to match the rest of their UI.

[nodakai]

Web frontent engineers would use "CSS Reset" scripts:

• http://www.cssreset.com/

[steveklabnik]

we are already using http://necolas.github.io/normalize.css/3.0.0/normalize.css

[tomjakubowski]

It doesn't really matter that we're using a CSS reset because CSS resets won't do what was originally asked in this issue.

If you set body/headline text color, then you have to set the background color too; otherwise you get conflicts with user and user agent stylesheets, like with Steam's browser. CSS resets don't usually set background or text colors on main elements, and they shouldn't.

[frewsxcv]

A screenshot of what this issue is: