Implement decoding of mouse events in Go

tools/tui/loop/api.go

@@ -74,6 +74,9 @@ type Loop struct {
 	// Called when a key event happens
 	OnKeyEvent func(event *KeyEvent) error
 
+	// Called when a mouse event happens
+	OnMouseEvent func(event *MouseEvent) error
+
 	// Called when text is received either from a key event or directly from the terminal
 	// Called with an empty string when bracketed paste ends
 	OnText func(text string, from_key_event bool, in_bracketed_paste bool) error