update webhook docs

Author: ysyneu

flashduty/en/1. On-call/8. Integrations/8.5 Webhooks/8.5.2 Incident webhook.md

@@ -98,7 +98,7 @@ acknowledged_at | int64| No | Acknowledgment time
 |      fields       |  map[string]interface{}  |  No   | Custom field key-value pairs, Key is string, Value can be any type depending on field type |
 |      creator      |  [Person](#Person)  |  No   | Creator information, exists only for manually created incidents |
 |       closer      |  [Person](#Person)  |  No   | Closer information, exists only for manually closed incidents |
-|    responders     | [][Responder](#Responder) |  No   | List of responder information |
+|    responders     | [][Responder](#Responder) |  No   | List of responder information, only exists after the incident is assigned. For i_new events, this value may be empty |
 |     alert_cnt     |        int64        |  No   | Number of associated alerts |
 |     channel_id     |        int64        |  No   | Channel ID, 0 means not belonging to any channel |
 |     channel_name   |        string        |  No   | Channel name |

flashduty/zh/1. On-call/5. 集成引导/8.5 Webhooks/8.5.2 故障 webhook.md

@@ -98,7 +98,7 @@ acknowledged_at | int64| 否 | 认领时间
 |      fields       |  map[string]interface{}  |  否  | 自定义字段 KV，Key 为字符串，Value 可能为任意类型，取决于字段类型|
 |      creator      |  [Person](#Person)  |  否  | 创建人员信息，仅手动创建故障时存在 |
 |       closer      |  [Person](#Person)  |  否  | 关闭人员信息，仅手动关闭故障时存在 |
-|    responders     | [][Responder](#Responder) |  否  | 处理人员信息列表 |
+|    responders     | [][Responder](#Responder) |  否  | 处理人员信息列表，仅故障被分派后存在。对于i_new事件，此值可能为空 |
 |     alert_cnt     |        int64        |  否  | 关联告警个数 |
 |     channel_id     |        int64        |  否  | 协作空间ID，为0代表不属于任何空间 |
 |     channel_name   |        string        |  否  | 协作空间名称 |