feat(formatter): format @starting-style (#2213)

crates/biome_css_formatter/src/css/statements/starting_style_at_rule.rs

@@ -1,10 +1,15 @@
 use crate::prelude::*;
-use biome_css_syntax::CssStartingStyleAtRule;
-use biome_rowan::AstNode;
+use biome_css_syntax::{CssStartingStyleAtRule, CssStartingStyleAtRuleFields};
+use biome_formatter::write;
+
 #[derive(Debug, Clone, Default)]
 pub(crate) struct FormatCssStartingStyleAtRule;
 impl FormatNodeRule<CssStartingStyleAtRule> for FormatCssStartingStyleAtRule {
     fn fmt_fields(&self, node: &CssStartingStyleAtRule, f: &mut CssFormatter) -> FormatResult<()> {
-        format_verbatim_node(node.syntax()).fmt(f)
+        let CssStartingStyleAtRuleFields {
+            starting_style_token,
+            block,
+        } = node.as_fields();
+        write!(f, [starting_style_token.format(), space(), block.format()])
     }
 }

crates/biome_css_formatter/tests/specs/css/atrule/starting_style.css

@@ -0,0 +1,18 @@
+@starting-style {
+    h1 {
+        background-color: transparent;
+    }
+
+
+    @layer          foo {
+        @starting-style {
+            background-color: transparent;
+        }
+
+        div {
+
+
+            height: 100px;
+        }
+    }
+}

crates/biome_css_formatter/tests/specs/css/atrule/starting_style.css.snap

@@ -0,0 +1,60 @@
+---
+source: crates/biome_formatter_test/src/snapshot_builder.rs
+info: css/atrule/starting_style.css
+---
+# Input
+
+```css
+@starting-style {
+    h1 {
+        background-color: transparent;
+    }
+
+
+    @layer          foo {
+        @starting-style {
+            background-color: transparent;
+        }
+
+        div {
+
+
+            height: 100px;
+        }
+    }
+}
+
+```
+
+
+=============================
+
+# Outputs
+
+## Output 1
+
+-----
+Indent style: Tab
+Indent width: 2
+Line ending: LF
+Line width: 80
+Quote style: Double Quotes
+-----
+
+```css
+@starting-style {
+	h1 {
+		background-color: transparent;
+	}
+
+	@layer foo {
+		@starting-style {
+			background-color: transparent;
+		}
+
+		div {
+			height: 100px;
+		}
+	}
+}
+```