qtquick: Add example of custom tabBar

Will do some styling in a follow up

examples/qtquick/customtabbar/CMakeLists.txt

@@ -0,0 +1,31 @@
+#
+# This file is part of KDDockWidgets.
+#
+# SPDX-FileCopyrightText: 2019-2022 Klarälvdalens Datakonsult AB, a KDAB Group company <info@kdab.com>
+# Author: Sergio Martins <sergio.martins@kdab.com>
+#
+# SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only
+#
+# Contact KDAB at <info@kdab.com> for commercial licensing options.
+#
+
+cmake_minimum_required(VERSION 3.7)
+project(qtquick_customtabbar)
+
+set(CMAKE_AUTOMOC ON)
+set(CMAKE_AUTORCC ON)
+set(CMAKE_INCLUDE_CURRENT_DIRS ON)
+
+if(NOT TARGET kddockwidgets)
+    # This will look for Qt, do find_package yourself manually before if you want
+    # to look for a specific Qt version for instance.
+    find_package(KDDockWidgets REQUIRED)
+endif()
+
+set(RESOURCES_EXAMPLE_SRC ${CMAKE_CURRENT_SOURCE_DIR}/resources_qtquick_example.qrc
+                          ${CMAKE_CURRENT_SOURCE_DIR}/../../dockwidgets/resources_example.qrc
+)
+
+add_executable(qtquick_customtabbar main.cpp ${RESOURCES_EXAMPLE_SRC})
+
+target_link_libraries(qtquick_customtabbar PRIVATE KDAB::kddockwidgets)