Document how to easily test new themes / colors

[TheKnarf]

Using an hash after the url you can easily test new color combinations.
Ex. http://localhost:3000/#1c110a-e4d6a7-e9b44c.

Use something like coolors.co/1c110a-e4d6a7-e9b44c, pick only three colors and then you can easily copy them over and test how the look in dave.

This needs documenting.