Document black and white color utilities

[aciccarello]

Do you want to request a feature or report a bug?

Feature Request

The docs should include descriptions of the black and white color helpers.

https://github.com/Teradata/covalent/blob/f305f117dd63ee1007f708c696891af7186bb27f/src/platform/core/common/styles/colors/_colors-light.scss#L292-L304

What is the expected behavior?

The colors and typography sections should list the black and white color options

What is the motivation / use case for changing the behavior?

Completeness of documentation

Other information

Also should look into the white-1/2 colors which seem to be defined exactly the same. https://github.com/Teradata/covalent/blob/f305f117dd63ee1007f708c696891af7186bb27f/src/platform/core/common/styles/colors/_colors-light.scss#L301-L302