feature: modify role icons

src/Discord.Net.Core/Entities/Roles/RoleProperties.cs

@@ -50,6 +50,11 @@ namespace Discord
         ///     This value may not be set if the role is an @everyone role.
         /// </remarks>
         public Optional<bool> Hoist { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the icon of the role.
+        /// </summary>
+        public Optional<Image> Icon { get; set; }
         /// <summary>
         ///     Gets or sets whether or not this role can be mentioned.
         /// </summary>

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

@@ -13,6 +13,8 @@ namespace Discord.API.Rest
         public Optional<uint> Color { get; set; }
         [JsonProperty("hoist")]
         public Optional<bool> Hoist { get; set; }
+        [JsonProperty("icon")]
+        public Optional<Image> Icon { get; set; }
         [JsonProperty("mentionable")]
         public Optional<bool> Mentionable { get; set; }
     }

src/Discord.Net.Rest/Entities/Roles/RoleHelper.cs

@@ -24,7 +24,8 @@ namespace Discord.Rest
                 Hoist = args.Hoist,
                 Mentionable = args.Mentionable,
                 Name = args.Name,
-                Permissions = args.Permissions.IsSpecified ? args.Permissions.Value.RawValue.ToString() : Optional.Create<string>()
+                Permissions = args.Permissions.IsSpecified ? args.Permissions.Value.RawValue.ToString() : Optional.Create<string>(),
+                Icon = args.Icon.IsSpecified ? args.Icon.Value.ToModel() : Optional<API.Image>.Unspecified
             };
             var model = await client.ApiClient.ModifyGuildRoleAsync(role.Guild.Id, role.Id, apiArgs, options).ConfigureAwait(false);