[MDC-List] Add a SASS mixin to set the ripple color

[akaSourav]

Feature Request

Sometimes it is required to display a list on the dark background without changing the surface color of the whole website. It will be really helpful if there is a SASS mixin for changing the ripple color of the list items.

Proposed solution

Make the _item-interactive-ripple($query) mixin of the evolution-list public and this mixin should take on-surface color argument for customizing the ripple color.

[joyzhong]

This should be possible with the upcoming theme API in development. Moving to backlog for now.