supported-color-schemes & prefers-color-scheme

[BenjaminHoegh]

Safari 12.2 add the support of two new CSS functions named prefers-color-scheme and supported-color-schemes

https://webkit.org/blog/8718/new-webkit-features-in-safari-12-1/

[Schweinepriester]

https://webkit.org/blog/8834/release-notes-for-safari-technology-preview-81/

Renamed supported-color-schemes to color-scheme (r244408)