Need an option for list of ignored properties

[Sigiller]

Now this module evaluate all color properties in css, but it may be very excessively. For example, box-shadow and text-shadow. Colors of this properties usually very close to text color, because there is should be an option to exclude some properties to make colorguard reporting more useful.

[ntwb]

Referencing the original stylelint report here: stylelint/stylelint#1495