Ladybird: Move Qt-specific classes and functions to a Qt subdirectory

This will help a lot with developing chromes for different UI frameworks
where we can see which helper classes and processes are really using Qt
vs just using it to get at helper data.

As a bonus, remove Qt dependency from WebDriver.

Ladybird/Qt/SettingsDialog.cpp

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2022, Filiph Sandström <filiph.sandstrom@filfatstudios.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "SettingsDialog.h"
+#include "Settings.h"
+#include <QCloseEvent>
+#include <QLabel>
+
+namespace Ladybird {
+
+extern Settings* s_settings;
+
+SettingsDialog::SettingsDialog(QMainWindow* window)
+    : m_window(window)
+{
+    m_layout = new QFormLayout(this);
+    m_new_tab_page = new QLineEdit(this);
+    m_ok_button = new QPushButton("&Save", this);
+
+    m_layout->addRow(new QLabel("Page on New Tab", this), m_new_tab_page);
+    m_layout->addWidget(m_ok_button);
+
+    QObject::connect(m_ok_button, &QPushButton::released, this, [this] {
+        close();
+    });
+
+    setWindowTitle("Settings");
+    setFixedWidth(300);
+    setFixedHeight(150);
+    setLayout(m_layout);
+    show();
+    setFocus();
+}
+
+void SettingsDialog::closeEvent(QCloseEvent* event)
+{
+    save();
+    event->accept();
+}
+
+void SettingsDialog::save()
+{
+    // FIXME: Validate data.
+    s_settings->set_new_tab_page(m_new_tab_page->text());
+}
+
+}