improve comment ,参考：https://github.com/huacnlee/autocorrect

pay/pay.go

@@ -9,12 +9,12 @@ import (
 	"github.com/silenceper/wechat/v2/pay/transfer"
 )
 
-// Pay 微信支付相关API
+// Pay 微信支付相关 API
 type Pay struct {
 	cfg *config.Config
 }
 
-// NewPay 实例化微信支付相关API
+// NewPay 实例化微信支付相关 API
 func NewPay(cfg *config.Config) *Pay {
 	return &Pay{cfg}
 }