Support for CSS nesting module

[blutorange]

https://www.w3.org/TR/css-nesting-1/

This is not a high priority for us, but I though I'd make an issue for tracking this feature. We use this parser to analyse custom CSS code written by users and they might start using the new nesting feature at some point. CSS nesting is supported by the latest browser versions https://caniuse.com/css-nesting

For example

.foo {
  color: red;

  &:hover {
    color: blue;
  }
}

[WARN] [17-07-23 11:47:42,579] [qtp600858818-449] (FormCssHelper.java:351) - Error while reading CSS file 'test.css', line 4, column 3: Encountered unexpected token: "&" <UNKNOWN>

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[blutorange]

It's not urgent, but I think this should stay open as CSS nesting is becoming more common and it would be great if it could be supported eventually.

[phax]

Sure, the bot did some bot stuff ... 🤷🏼