feat(css): add support for parsing and formatting the CSS if function (#8111)

Co-authored-by: Carson McManus <[email protected]>

Author: ryan-m-walker

.changeset/seven-words-trade.md

@@ -0,0 +1,13 @@
+---
+"@biomejs/biome": patch
+---
+
+Added support for parsing and formatting the [CSS if function](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Values/if).
+
+***Example***
+
+``` css
+.basic-style {
+  color: if(style(--scheme: dark): #eeeeee; else: #000000;);
+}
+```