`importFrom` should support ESM

[scinos]

Looking at the docs, exportTo supports exporting a ESM module if the file ends with .mjs.

However importFrom doesn't seem to support importing .mjs files (

postcss-custom-properties/src/lib/get-custom-properties-from-imports.js

Line 85 in 9b46ae8

if (type === 'js') {

).

[Antonio-Laguna]

Fixed as of 12.1.0

[romainmenke]

Note : only works when executing postcss from a module context.