Assigning things into Data throws if the key or value isn't Serializable. this should be documented.

The sourcecode of ListDictionaryInternal is explicit:
```cs
if (key == null)
{
throw new ArgumentNullException("key", Environment.GetResourceString("ArgumentNull_Key"));
}
if (!key.GetType().IsSerializable)
{
throw new ArgumentException(Environment.GetResourceString("Argument_NotSerializable"), "key");
}
if (value != null && !value.GetType().IsSerializable)
{
throw new ArgumentException(Environment.GetResourceString("Argument_NotSerializable"), "value");
}
```

i think this should at least be mentioned in the documentation, e.g. somewhere here:
https://learn.microsoft.com/en-us/dotnet/api/system.exception.data?view=netframework-4.8#system-exception-data