a11y-constract misleading

[Shaun McCance <shaunm gnome org>]

I think a11y-contrast is misleading. It starts with
"To adjust the contrast of things on the screen".
That makes me think it's going to change the color
contrast on my monitor. The title doesn't help.

I think we need an introductory paragraph about what
this actually does, and why you would actually want
to use it. If no one else does, I'll take a crack at
it tomorrow.

If you do want to work on this or any other a11y page,
the people in #a11y are very friendly and they know
what they're talking about. We all need to get in the
habit of talking to subject matter experts more often.

Thanks,
Shaun