User is allowed to try add effects without the "scene" component

1. Create a new Empty project
2. Add QtQuick3D -module
3. Press the "Add an instance" option for an effect:
   1. UI shows that the effect is imported, but nothing appears on the 3D view, because effect are only usable under "scene" component
4. Drag and drop an effect to the 3D view
   1. User is allowed to drag the effect to the 3D view, but it will not appear there without the "scene" component
5. Add the view3D -component to the project and now press the "Add an instance" -option for the effect:
   1. You will see, that the effect will become available. If you tried to add two effects without the "scene" -component, they both will become available

See the video for better understanding:

qtdesignstudio_Ov0kAq3FcY.mp4

It might be better, that it would read under the Effects -tab, that to use effects, user must add the QtQuick3D -module AND also add the view3D -component. Now it only mentions, that user needs to add the QtQuick3D -module to use the Content Library.