Add 'zero' event

Close #3263

src/tui/tui.go

@@ -94,6 +94,7 @@ const (
 	Load
 	Focus
 	One
+	Zero
 
 	AltBS
 
@@ -283,6 +284,15 @@ type Event struct {
 	MouseEvent *MouseEvent
 }
 
+func (e Event) Is(types ...EventType) bool {
+	for _, t := range types {
+		if e.Type == t {
+			return true
+		}
+	}
+	return false
+}
+
 type MouseEvent struct {
 	Y      int
 	X      int