Support @property declarations

[jedrichards]

The following code reports a lint error, with this plugin. It would be nice to support the @property declaration though, both inline, and via any declarations found via importFrom.

@property --color {
  initial-value: #f00;
  syntax: '<color>';
}

.thing {
  color: var(--color);
}

Thank you!

[evtk]

+1 for this feature request.