Highlight punctuation as HighlightTag::Operator

crates/ra_ide/src/syntax_highlighting.rs

@@ -553,6 +553,7 @@ fn highlight_element(
         T![!] if element.parent().and_then(ast::MacroCall::cast).is_some() => {
             Highlight::new(HighlightTag::Macro)
         }
+        p if p.is_punct() => HighlightTag::Operator.into(),
 
         k if k.is_keyword() => {
             let h = Highlight::new(HighlightTag::Keyword);