Fix: Allow deserialize pretty-printed JSON with type information

When testing our services we realized that a pretty-printed JSON contain __type information cannot be properly deserialized (there can be whitespaces before __type):

```c#
  [TestFixture]
    public class Class1
    {
        class MyClass : IComparable
        {
            public int CompareTo(object obj)
            {
                return 0;
            }
        }

        [Test]
        [TestCase("[{'__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[{ '__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[{\n'__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[{\t'__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[ {'__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[\n{'__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[\t{'__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[ { '__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[\n{\n'__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[\t{\t'__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[{'__type':'MyTest.Class1+MyClass'} ]")]
        [TestCase("[{ '__type':'MyTest.Class1+MyClass'}\t]")]
        [TestCase("[{\n'__type':'MyTest.Class1+MyClass'}\n]")]
        [TestCase("[{\t'__type':'MyTest.Class1+MyClass' }]")]
        [TestCase("[ {'__type':'MyTest.Class1+MyClass'\t}]")]
        [TestCase("[\n{'__type':'MyTest.Class1+MyClass'\n}]")]
        [TestCase("[\t{'__type':'MyTest.Class1+MyClass'\t}\n]")]
        [TestCase("[ { '__type':'MyTest.Class1+MyClass', }]")]
        [TestCase("[\n{\n'__type':'MyTest.Class1+MyClass'}]")]
        [TestCase("[\t{\t'__type':'MyTest.Class1+MyClass'}]")]
        public void TypeAttrInObject(string json)
        {
            json = json.Replace('\'', '"');
            var deserDto = JsonSerializer.DeserializeFromString<List<IComparable>>(json);
            Console.WriteLine(json);
            Assert.IsNotNull(deserDto);
            Assert.AreEqual(1, deserDto.Count);
            Assert.IsNotNull(deserDto[0]);
        }

    }
```