[Feature request] Add "transparent" color

[derhuebiii]

Description

It would be nice if we could also add "transparent" / transparency to choose. See example screenshot:

Expected outcome

Steps to reproduce

Could be implemented by adding a field like in my screenshot when a color named "transparent/transparency" is added.

Example css for stripes

background: white;
    background-image: url(data:image/svg+xml;base64,PHN2ZyB4bWxucz0naHR0cDovL3d3dy53My5vcmcvMjAwMC9zd…05LDExIGwyLC0yJyBzdHJva2U9J2JsYWNrJyBzdHJva2Utd2lkdGg9JzEnLz4KPC9zdmc+Cg==);
    background-repeat: repeat;
    color: transparent;

from https://iros.github.io/patternfills/sample_css.html