Custom Function Parser 
Implemented from : https://www.w3.org/TR/mediaqueries-5/
Usage
Add Custom Function Parser to your project:
npm install @csstools/custom-function-parser @csstools/css-parser-algorithms @csstools/css-tokenizer --save-dev
Custom Function Parser depends on our CSS tokenizer and parser algorithms.
It must be used together with @csstools/css-tokenizer and @csstools/css-parser-algorithms.
// TODO