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/PluginRepl.hpp

@@ -0,0 +1,91 @@
+#pragma once
+
+#ifdef CHATTERINO_HAVE_PLUGINS
+#    include "widgets/BaseWindow.hpp"
+
+#    include <boost/signals2/connection.hpp>
+#    include <QString>
+#    include <QTextBlockFormat>
+#    include <QTextCharFormat>
+#    include <sol/forward.hpp>
+
+class QTextEdit;
+class QTextCharFormat;
+class QTextBlockFormat;
+
+namespace chatterino::lua::api {
+enum class LogLevel;
+}  // namespace chatterino::lua::api
+
+namespace chatterino {
+
+class Plugin;
+class SvgButton;
+class PixmapButton;
+
+class PluginRepl : public BaseWindow
+{
+public:
+    PluginRepl(QString id, QWidget *parent = nullptr);
+
+    static QFont currentFont();
+
+protected:
+    void themeChangedEvent() override;
+
+private:
+    struct LogOptions {
+        /// Maximum number of items to show in tables.
+        size_t maxItems = 10;
+    };
+
+    void tryRun(QString code);
+    void logResult(const sol::protected_function_result &res,
+                   const LogOptions &opts);
+
+    void log(std::optional<lua::api::LogLevel> level, const QString &text);
+
+    void tryUpdate();
+    void setPlugin(Plugin *plugin);
+
+    void updateFont();
+    void updatePinned();
+
+    QString id;
+    Plugin *plugin = nullptr;
+
+    boost::signals2::scoped_connection pluginDestroyConn;
+    boost::signals2::scoped_connection pluginLogConn;
+    boost::signals2::scoped_connection pluginLoadedConn;
+
+    bool isPinned = false;
+
+    struct {
+        QTextEdit *input = nullptr;
+        QTextEdit *output = nullptr;
+        SvgButton *clear = nullptr;
+        SvgButton *reload = nullptr;
+        PixmapButton *pin = nullptr;
+    } ui;
+
+    struct {
+        QTextCharFormat self;
+        QTextCharFormat debug;
+        QTextCharFormat info;
+        QTextCharFormat warning;
+        QTextCharFormat error;
+    } charFormats;
+    struct {
+        QTextBlockFormat self;
+        QTextBlockFormat debug;
+        QTextBlockFormat info;
+        QTextBlockFormat warning;
+        QTextBlockFormat error;
+    } blockFormats;
+
+    QFont font;
+};
+
+}  // namespace chatterino
+
+#endif