feature: Add user public flags (#1722)

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

@@ -29,5 +29,7 @@ namespace Discord.API
         public Optional<PremiumType> PremiumType { get; set; }
         [JsonProperty("locale")]
         public Optional<string> Locale { get; set; }
+        [JsonProperty("public_flags")]
+        public Optional<UserProperties> PublicFlags { get; set; }
     }
 }