Scale up font contrast

[charafau]

From Hacker news discussion someone mention font color readability.

Great stuff but can you please scale up font contrast a bit?
Just removing this body { color: #586E75 } altogether makes your page readable.

I personally think that it's good idea. Screenshots for reference.

Now:

After change:

[SethTisue]

SGTM — would you like to make a PR?

[SethTisue]

the corresponding issue in the docs site repo is scala/docs.scala-lang#569

[SethTisue]

I'm not sure if this got addressed in #606 or not

[heathermiller]

Fixed in #606