Improve Qt Quick I18N example

Separating the example suggestion from the original ticket: QTBUG-127411

(6) We should improve the [Qt Quick I18N example|https://doc.qt.io/qt-6/qtqml-qml-i18n-example.html.]

What I have in mind is to make this example much like Qt for MCUs' thermo demo, where it uses Qt.uiLanguage to dynamically change the languages of the texts. The issue in the current Qt Quick I18N example is that it doesn't use Qt.uiLanguage to dynamically translate the texts, which is the basic usecase of any realistic i18n app. The enhanced example should show how the users can dynamically translate, how they should write CMakeLists.txt for it and most importantly, they should enable "<target_name>_lrelease" and "<target_name>_lupdate" targets in Build setting for the Kit they use on Qt Creator to update the .ts and .qm files(Of course, we need a lot of screenshots to avoid any possible misunderstanding and confusion). Ideally, we should add an internationalization & localization tutorial documentation which is based on this enhanced example. The tutorial should also contain how to use Linguist on this particular app, meaning, a user can just read and work on this tutorial to fully understand the basics on how they can make their own i18n app. This example may contain other use cases too, such as plural translation.