Add special specs of the app entry point main{}

What?

main.cpp of the Qt project that is going to be used by QtQuickView is not compatible with the default one that most of our tools (Qt Creator and Qt Design Studio)

Why?

Although the application library has main{} entry point, they should not instantiate a Quick window, as QtQuickView is supposed to create the main window. But the main evenloop still needs to be created by QGuiApplication::exec() in side main{}.

The user of QtQuickView, is still able to add more initialization to the entry point of the library though. For instance if they would like to register types, load external resources, register JNI function or any other case other than instantiating a quick window.

How?

For now, before adding support in our tools, this can be documented so that if a user creates a QML project using any other tool than the Qt Tools for Android Studio, they have enough information to modify the main.cpp accordingly.