Description

Named colors with uppercase letters aren't recognized by the library.

Steps to reproduce

• Load the library (using Codepen, a project, etc.): import cs from "color-string"
• Call the library with a named color with an uppercase letter: cs.get("Blue")
• Note that a null value is returned

Notes

• Though these named colors are supposed to be lowercase by spec, it seems reasonable (and user friendly) to handle uppercase letters as well
• A call to toLowerCase for all methods where a string is passed in should take care of it