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/LibSyntax/Highlighter.h

@@ -41,6 +41,8 @@ public:
 
     virtual Language language() const = 0;
     StringView language_string(Language) const;
+    virtual Optional<StringView> comment_prefix() const = 0;
+    virtual Optional<StringView> comment_suffix() const = 0;
     virtual void rehighlight(Palette const&) = 0;
     virtual void highlight_matching_token_pair();