Basics of the build and install steps for the Qt 3D Studio runtime are not documented

Current docs about the 3D integration only mention the use of Qt 3D Studio as a tool: https://doc-snapshots.qt.io/neptune3ui-dev/neptune3ui-3d-integration.html

Despite of the fact that use of the Qt 3D Studio runtime is not directly mentioned, we now need an explicit description of the basic steps what a developer should do to experience our 3D integration on the screen.

Unfortunately, the Qt 3D Studio does not describe those steps either: https://doc.qt.io/qt3dstudio/runtime/qt3d-runtime-index.html. It assumes, a user would get everything pre-built from the installer.

We shall not repeat things which should be documented in Qt 3D Studio, but we have to provide at least basic steps incl. essential information as the version number of the runtime which is used