feat(scan): add Scanner interface

[monkey92t]

Add Scanner interface, scanner is an interface for custom decoding:

See #2298 #2295 #1631

type TimeValue struct {
	time.Time
}

func (t *TimeValue) ScanRedis(s string) (err error) {
	t.Time, err = time.Parse(time.RFC3339Nano, s)
	return
}

type Data struct {
	Name      string     `redis:"name"`
	LoginTime TimeValue  `redis:"login_time"`
}

var d Data
err := client.MGet(ctx, "name", "login_time").Scan(&d)