Provide the entire syntax and configuration entries for QT_QPA_EGLFS_KMS_CONFIG

link : https://doc.qt.io/qt-6/embedded-linux.html#custom-configuration

This page introduces the json file which a user can create to configure the behavior of KMS/DRM.

I just shows an example snippet but it would be much better if there's a table or something which shows all the configurable fields and possible values for each, plus syntax rules.

Currently, readers(at least myself) can get the impression that the snippet is just one example and there are some other possible configurations. Even if that's not the case, giving that kind of impression is not good anyway so how the information is presented should have room for improvement.