Add info about Extended Scene Environment properties

Our docs for extended scene environment don't describe many of the properties of the extended scene environment, for example FXAA, and the tooltips don't add much info (i.e. FXAA = Enables fast approximate antialiasing).

https://doc-snapshots.qt.io/qtdesignstudio/studio-3d-scene-environment.html

We should either describe these properties in our documentation or provide better tooltips.