Add dingtalk webhook (#2777)

* add dingtalk webhook type

* add vendor

* some fixes

* fix name check

* fix name check & improvment

vendor/github.com/lunny/dingtalk_webhook/LICENSE

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+Copyright (c) 2016 The Gitea Authors
+Copyright (c) 2015 The Gogs Authors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

vendor/github.com/lunny/dingtalk_webhook/README.md

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+# 非官方 Dingtalk webhook Golang SDK
+
+## 此工程仅封装了 Dingtalk 的 webhook 部分的请求
+
+## 使用
+
+首先在dingtalk中创建一个机器人，将accessToken拷贝出来，然后执行下面方法即可
+
+```Go
+webhook := dingtalk.Webhook(accessToken)
+webhook.SendTextMsg("这是一个没有AT的文本消息", false)
+```
+
+## License
+
+This project is licensed under the MIT License.
+See the [LICENSE](https://github.com/lunny/webhook_dingtalk/blob/master/LICENSE) file
+for the full license text.