Initial import. Most things seem working.

This includes an abortive attempt to do a gtk4 dialog (which I don't
think is possible, as gtk4 doesn't allow embedding toplevels anymore),
and an iced dialog, which I just never started writing.

dialog-iced/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "bscreensaver-dialog-iced"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+bscreensaver-util = { path = "../util" }
+xcb = { version = "1.1", features = ["randr"] }