<url>: mention which properties have CORS restrictions

### MDN URL

https://developer.mozilla.org/en-US/docs/Web/CSS/url

### What specific section or headline is this issue about?

New section

### What information was incorrect, unhelpful, or incomplete?

This page doesn't say which properties accept `file:` URLs and which don't. From https://github.com/mdn/content/issues/29106, it seems all new properties have CORS requirements.

### What did you expect to see?

Two things:

- On the `` page, two lists of properties that have CORS restrictions and those that don't
- For those properties with CORS, the same note as https://github.com/mdn/content/pull/34938 added to the property value DL.

### Do you have any supporting links, references, or citations?

_No response_

### Do you have anything more you want to share?

This likely depends on https://github.com/mdn/content/issues/35029 so we can document it on `` instead of `url()`, but we may also just document it on this page first, and then decide where to put this information later.