Reducing ISTF spec to a CSS subset for consistency

[kof]

CSS has lots of inconsistencies, driven by DX they thought they are optimizing. For e.g. url can be defined as a CSS string, as a url token and as a url function.

In ISTF we

1. don't need many ways to describe the same
2. want to reduce complexity for transformation and strinfigification steps

Lets discuss here all possible things we would want to describe in one consistent way.

[kof]

1. For the URL, I would always use a url function