Add RollupPropertyItem type

Author: KoditkarVedant

Src/Notion.Client/Models/PropertyItems/RollupPropertyItem.cs

@@ -0,0 +1,29 @@
+using System.Collections.Generic;
+using Newtonsoft.Json;
+
+namespace Notion.Client
+{
+    public class RollupPropertyItem : SimplePropertyItem
+    {
+        public override string Type => "rollup";
+
+        [JsonProperty("rollup")] public Data Rollup { get; set; }
+
+        public class Data
+        {
+            [JsonProperty("type")] public string Type { get; set; }
+
+            [JsonProperty("function")] public string Function { get; set; }
+
+            [JsonProperty("number")] public double? Number { get; set; }
+
+            [JsonProperty("date")] public Date Date { get; set; }
+
+            [JsonProperty("array")] public IEnumerable<Dictionary<string, object>> Array { get; set; }
+
+            [JsonProperty("unsupported")] public Dictionary<string, object> Unsupported { get; set; }
+
+            [JsonProperty("incomplete")] public Dictionary<string, object> Incomplete { get; set; }
+        }
+    }
+}

Src/Notion.Client/Models/PropertyItems/SimplePropertyItem.cs

@@ -1,5 +1,4 @@
-using System.Collections;
-using JsonSubTypes;
+using JsonSubTypes;
 using Newtonsoft.Json;
 
 namespace Notion.Client
@@ -24,6 +23,7 @@ namespace Notion.Client
     [JsonSubtypes.KnownSubType(typeof(RichTextPropertyItem), "rich_text")]
     [JsonSubtypes.KnownSubType(typeof(PeoplePropertyItem), "people")]
     [JsonSubtypes.KnownSubType(typeof(RelationPropertyItem), "relation")]
+    [JsonSubtypes.KnownSubType(typeof(RollupPropertyItem), "rollup")]
     public abstract class SimplePropertyItem : IPropertyItemObject
     {
         public string Object => "property_item";