Docs improvment

[ai]

Hi. Thanks for the great plugin!

I have a few ideas how we can improve docs:

1. Maybe we can put a link why antialiasing is needed for webkit in light colors (I use Linux, maybe I didn’t have the same problem).
2. Screenshots could be even better.

It is good add-and-forget plugin, I think ti promote it in PostCSS twitter, but with some description of the reason, promotion could be much more effective.