Window event callbacks now take a WindowEventContext

Improved event example

v3/pkg/application/context_window_event.go

@@ -0,0 +1,14 @@
+package application
+
+var blankWindowEventContext = &WindowEventContext{}
+
+type WindowEventContext struct {
+	// contains filtered or unexported fields
+	data map[string]any
+}
+
+func newWindowEventContext() *Context {
+	return &Context{
+		data: make(map[string]any),
+	}
+}