* Part of https://github.com/emilk/egui/issues/3524
This is a breaking change, as it changes the how embedded viewports
work.
Before it was up to the user to display a `egui::Window` if they wanted.
Now egui creates an `egui::Window` for you, so you only need to add the
contents.
To signal this change in behavior, `ViewportClass::Embedded` is gone and
is now called `ViewportClass::EmbeddedWindow`.
9487dc35ec
