Scene ambiant lighting

[Nibor62]

I,

I think it could be nice to talk about the ambient lighting of a scene into the book, as it can be surprising to get lit scenes when you have no lights and don't known about this feature.
However I dunno where to put it, since the book only talk about light in the light node, but ambient light isn't a node.

Maybe directly into the 2.2 Scene and with a note in 2.2.4 Light pointing to it ?