feat: add REPL for plugins (#6120)

This can be enabled by setting the `.plugins.repl.enabled` setting to true


Close Chatterino and make a backup of your settings.json before attempting any modifications.
```json5
{
  "plugins": {
    "repl": {
      "enabled": true,
    },
  },
}
```

src/widgets/settingspages/SettingWidget.cpp

@@ -10,6 +10,7 @@
 
 #include <QBoxLayout>
 #include <QCheckBox>
+#include <QFontDialog>
 #include <QFormLayout>
 #include <QLabel>
 #include <QLineEdit>
@@ -393,6 +394,45 @@ SettingWidget *SettingWidget::lineEdit(const QString &label,
     return widget;
 }
 
+SettingWidget *SettingWidget::fontButton(const QString &label,
+                                         QStringSetting &familySetting,
+                                         std::function<QFont()> currentFont,
+                                         std::function<void(QFont)> onChange)
+{
+    auto *widget = new SettingWidget(label);
+
+    auto *lbl = new QLabel(label + ":");
+
+    auto *button = new QPushButton(currentFont().family());
+
+    widget->hLayout->addWidget(lbl);
+    widget->hLayout->addStretch(1);
+    widget->hLayout->addWidget(button);
+
+    familySetting.connect(
+        [button, currentFont](const auto &) {
+            button->setText(currentFont().family());
+        },
+        widget->managedConnections);
+
+    QObject::connect(button, &QPushButton::clicked,
+                     [widget, currentFont{std::move(currentFont)},
+                      onChange{std::move(onChange)}]() {
+                         bool ok = false;
+                         auto font =
+                             QFontDialog::getFont(&ok, currentFont(), widget);
+                         if (ok)
+                         {
+                             onChange(font);
+                         }
+                     });
+
+    widget->actionWidget = button;
+    widget->label = lbl;
+
+    return widget;
+}
+
 SettingWidget *SettingWidget::setTooltip(QString tooltip)
 {
     assert(!tooltip.isEmpty());