Ladybird: Rudimentary tabbed browsing support

This patch removes the browser WebView from the window and places it
inside a Tab object, all wrapped up in a QT tab control. So far you can
create tabs, but can't close them.

Ladybird/Tab.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2022, Matthew Costa <ucosty@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include "WebView.h"
+#include <QBoxLayout>
+#include <QLineEdit>
+#include <QToolBar>
+#include <QWidget>
+
+class Tab final : public QWidget {
+    Q_OBJECT
+public:
+    explicit Tab(QMainWindow* window);
+
+    WebView& view() { return *m_view; }
+
+public slots:
+    void location_edit_return_pressed();
+    void page_title_changed(QString);
+    void page_favicon_changed(QIcon);
+    void reload();
+
+signals:
+    void title_changed(int id, QString);
+    void favicon_changed(int id, QIcon);
+
+private:
+    QBoxLayout* m_layout;
+    QToolBar* m_toolbar { nullptr };
+    QLineEdit* m_location_edit { nullptr };
+    WebView* m_view { nullptr };
+    QMainWindow* m_window { nullptr };
+
+    int tab_index();
+};