feat(work): 新增企业邮箱新邮件提醒相关接口

src/SKIT.FlurlHttpClient.Wechat.Work/Models/CgibinExmail/Mail/CgibinExmailMailGetNewCountRequest.cs

@@ -0,0 +1,15 @@
+namespace SKIT.FlurlHttpClient.Wechat.Work.Models
+{
+    /// <summary>
+    /// <para>表示 [POST] /cgi-bin/exmail/mail/get_newcount 接口的请求。</para>
+    /// </summary>
+    public class CgibinExmailMailGetNewCountRequest : WechatWorkRequest
+    {
+        /// <summary>
+        /// 获取或设置成员账号。
+        /// </summary>
+        [Newtonsoft.Json.JsonProperty("userid")]
+        [System.Text.Json.Serialization.JsonPropertyName("userid")]
+        public string UserId { get; set; } = string.Empty;
+    }
+}

src/SKIT.FlurlHttpClient.Wechat.Work/Models/CgibinExmail/Mail/CgibinExmailMailGetNewCountResponse.cs

@@ -0,0 +1,15 @@
+namespace SKIT.FlurlHttpClient.Wechat.Work.Models
+{
+    /// <summary>
+    /// <para>表示 [POST] /cgi-bin/exmail/mail/get_newcount 接口的响应。</para>
+    /// </summary>
+    public class CgibinExmailMailGetNewCountResponse : WechatWorkResponse
+    {
+        /// <summary>
+        /// 获取或设置新邮件数。
+        /// </summary>
+        [Newtonsoft.Json.JsonProperty("count")]
+        [System.Text.Json.Serialization.JsonPropertyName("count")]
+        public int NewCount { get; set; }
+    }
+}