LibSyntax: Teach each highlighter about it's comment syntax

Author: https://github.com/lanmonster 🔰
Commit: 31290c8527
Pull-request: https://github.com/SerenityOS/serenity/pull/15803
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/Zaggy1024
Reviewed-by: https://github.com/idispatch

Userland/Libraries/LibCpp/SemanticSyntaxHighlighter.h

@@ -25,6 +25,9 @@ public:
     virtual bool is_navigatable(u64 token) const override;
 
     virtual Syntax::Language language() const override { return Syntax::Language::Cpp; }
+    virtual Optional<StringView> comment_prefix() const override { return "//"sv; }
+    virtual Optional<StringView> comment_suffix() const override { return {}; }
+
     virtual void rehighlight(Palette const&) override;
 
     void update_tokens_info(Vector<CodeComprehension::TokenInfo>);