Footer is an app-chrome control (bottom area) for hints, status, and key gesture reminders.
Footer is typically used as the bottom bar of a DockLayout.
var root = new DockLayout()
.Content(new TextArea("Main content"))
.Bottom(new Footer()
.Left("Tab focus")
.Center("Ready")
.Right("Ctrl+Q quit"));
HorizontalAlignment = Align.Stretch, VerticalAlignment = Align.StartLeft, Center, Right: slot visuals arranged on a single row