Export colors as a constant

[justinanastos]

This will require we change how we import colors.

Old:

import * as colors from '@apollo/space-kit/colors';

New:

import { colors } from '@apollo/space-kit/colors';

The import * is awkward and it's a pain to remember when we need that. So let's never do it.

[mayakoneval]

sweet lgtm. please ping me when published so I can update my engine prs!

[timbotnik]

i think this negates any possibility of tree-shaking based on only importing a subset of colors, but everyone always doing import * coupled with the fact that we are only talking about a few constant definitions indicates to me that this is not a very serious objection.