feat: include more data when copying messages as JSON (#5600)

src/messages/MessageColor.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <QColor>
+#include <QString>
 
 namespace chatterino {
 class Theme;
@@ -13,6 +14,8 @@ struct MessageColor {
 
     const QColor &getColor(Theme &themeManager) const;
 
+    QString toString() const;
+
 private:
     Type type_;
     QColor customColor_;