Implemented scene events and callback handlers for those events. Manager defaults also added.

scene.go

@@ -2,8 +2,23 @@ package groovy
 
 import "github.com/hajimehoshi/ebiten/v2"
 
+type SceneEvent int64
+
+const (
+	NOOP      SceneEvent = 0
+	RESET     SceneEvent = 1 // reset to initial scene
+	RELOAD    SceneEvent = 3 // reload current scene
+	COMPLETED SceneEvent = 4 // current scene has completed
+	ENDGAME   SceneEvent = 5 // shutdown all scenes
+)
+
 type Scene interface {
 	Update() error
 	Draw(screen *ebiten.Image)
-	Completed() bool
+	SetEventHandler(e SceneEvent, f func())
+}
+
+type ArgoScale interface {
+	Draw(screen *ebiten.Image)
+	GetSceneEvents() []SceneEvent
 }