refactor: consolidate font picking into one dialog (#6531)

Instead of three separate dropdowns in the setting dialog, we now expose a single label + button combo for modifying the font.
When the button is pressed, we open a custom font dialog allowing the user to customize the font family, font size, and font weight.

Reviewed-by: nerix <nerixdev@outlook.de>
Reviewed-by: pajlada <rasmus.karlsson@pajlada.com>

src/widgets/helper/FontSettingWidget.hpp

@@ -0,0 +1,35 @@
+#pragma once
+
+#include "common/ChatterinoSetting.hpp"
+#include "util/SignalListener.hpp"
+
+#include <QLabel>
+#include <QWidget>
+
+namespace chatterino {
+
+class FontSettingDialog;
+
+/// FontSettingWidget includes a label showing the current font and its size, with a button
+/// that opens a FontSettingDialog
+class FontSettingWidget : public QWidget
+{
+public:
+    FontSettingWidget(QStringSetting &family, IntSetting &size,
+                      IntSetting &weight, QWidget *parent = nullptr);
+
+private:
+    void updateCurrentLabel();
+    void showDialog();
+
+    FontSettingDialog *dialog = nullptr;
+
+    QStringSetting &familySetting;
+    IntSetting &sizeSetting;
+    IntSetting &weightSetting;
+
+    QLabel *currentLabel;
+    SignalListener listener;
+};
+
+}  // namespace chatterino