Clearly describe the bug

declaration-property-unit-allowed-list trips on SCSS function contents. Specifically color functions, which it should ignore.

Which rule, if any, is the bug related to?

declaration-property-unit-allowed-list

What code is needed to reproduce the bug?

$input-border: #639;

button {
  border: 1px solid lighten($input-border, 20%);
}

To reproduce:

$ npm pack styled-jsx@3.2.4
npm notice
npm notice 📦  styled-jsx@3.2.4
npm notice === Tarball Contents ===
npm notice 6.1kB  dist/.DS_Store
npm notice 599B   dist/_constants.js
npm notice 22.3kB dist/_utils.js
npm notice 8.2kB  dist/babel-external.js
npm notice 46B    babel-test.js
npm notice 753B   dist/babel-test.js
npm notice 41B    babel.js
npm notice 10.4k

Recently @devrnt opened up a PR to improve the setup with a theme(#189) and I realised that it'll be awesome to have that section expanded for each case.