Add SyncPermissionsAsync to Sync Child Channels with its Parent (#1159)

* Initial implementation

* Adjust according to comments

See: 6e76b45713 (diff-58466c35787d448266d026692e467baa)

src/Discord.Net.Rest/API/Common/Overwrite.cs

@@ -1,4 +1,4 @@
-#pragma warning disable CS1591
+#pragma warning disable CS1591
 using Newtonsoft.Json;
 
 namespace Discord.API

src/Discord.Net.Rest/API/Rest/ModifyGuildChannelParams.cs

@@ -1,4 +1,4 @@
-#pragma warning disable CS1591
+#pragma warning disable CS1591
 using Newtonsoft.Json;
 
 namespace Discord.API.Rest
@@ -12,5 +12,7 @@ namespace Discord.API.Rest
         public Optional<int> Position { get; set; }
         [JsonProperty("parent_id")]
         public Optional<ulong?> CategoryId { get; set; }
+        [JsonProperty("permission_overwrites")]
+        public Optional<Overwrite[]> Overwrites { get; set; }
     }
 }