Record derive helper attributes, resolve them in IDE layer

crates/ide/src/syntax_highlighting.rs

@@ -107,6 +107,7 @@ pub struct HlRange {
 // builtinType:: Emitted for builtin types like `u32`, `str` and `f32`.
 // comment:: Emitted for comments.
 // constParameter:: Emitted for const parameters.
+// deriveHelper:: Emitted for derive helper attributes.
 // enumMember:: Emitted for enum variants.
 // generic:: Emitted for generic tokens that have no mapping.
 // keyword:: Emitted for keywords.