Replace the obsolete JsonSerializerOption IgnoreNullValues with the n…

…ewer equivalent DefaultIgnoreCondition.

README.md

@@ -15,7 +15,7 @@ To retain the old settings use the following configuration when adding Blazored
 builder.Services.AddBlazoredLocalStorage(config =>
 {
     config.JsonSerializerOptions.DictionaryKeyPolicy = JsonNamingPolicy.CamelCase;
-    config.JsonSerializerOptions.IgnoreNullValues = true;
+    config.JsonSerializerOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull;
     config.JsonSerializerOptions.IgnoreReadOnlyProperties = true;
     config.JsonSerializerOptions.PropertyNameCaseInsensitive = true;
     config.JsonSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;