HackStudio: Abstract over syntax highlighter

Author: https://github.com/oriko1010
Commit: 137d68a2ae
Pull-request: https://github.com/SerenityOS/serenity/pull/1429
Reviewed-by: https://github.com/awesomekling

Libraries/LibGUI/SyntaxHighlighter.h

@@ -22,6 +22,9 @@ public:
     virtual void rehighlight() = 0;
     virtual void highlight_matching_token_pair() = 0;
 
+    virtual bool is_identifier(void*) const { return false; };
+    virtual bool is_navigatable(void*) const { return false; };
+
     void attach(TextEditor& editor);
     void detach();
     void cursor_did_change();