Default font improvements

[arraypress]

I made some revisions to the font CSS which looks a lot better on the theme:

body, button, input, select, textarea {
    color: #696969;
    font-family: "Helvetica Neue",Helvetica,Arial,sans-serif;
    font-size: 1.1rem;
    line-height: 1.5rem;
    text-rendering: optimizeLegibility;
}

This obviously looks better for OS X users but has the fallbacks in place as like before for compatibility.

[arraypress]

I also applied to the headers as well!

[amdrew]

Currently Themedd uses text-rendering: geometricPrecision;. Gecko actually ignores this and uses optimizeLegibility anyway. We may however remove text-rendering altogether since there are some performance issues on mobile devices and the difference IMO is very, very minor. I think it affects kerning at certain font-sizes for certain fonts?

Themedd is obviously BYOF (Bring Your Own Font) but I agree that "Helvetica Neue",Helvetica,Arial,sans-serif; is a better default font stack than Arial, Verdana, sans-serif; 👍

[amdrew]

Implemented new font stack above, tagging for future release so we can revisit the text-rendering.

[arraypress]

What do you think of this font stack @amdrew?

font-family: system, -apple-system, BlinkMacSystemFont, 'Helvetica Neue', 'Lucida Grande', 'Arial', 'Verdana', "Sans-Serif"

[amdrew]

@davidsherlock I like the idea of using native fonts, definitely looks a lot nicer, at least on my mac. Will need to do some testing to see how this looks on PCs etc.

Small issue with the stack above, "Sans-Serif" shouldn't have quotes since it's not a specific font.

Will revisit this after 1.0.

[arraypress]

Just found another good looking font stack (posting here for reference):

-apple-system,BlinkMacSystemFont,San Francisco,Helvetica Neue,Helvetica,Ubuntu,Roboto,Noto,Segoe UI,Arial,sans-serif