Add support for numeric json class discriminators

[JesseCorbett]

What is your use-case and why do you need this feature?

Many APIs such as Discord use type codes, which align very closely to this library's JsonClassDiscriminator feature. However, these type codes are frequently numeric instead of strings, which makes them incompatible with this library without complex workarounds.

Describe the solution you'd like

I would prefer a solution which adds an option to specify the serialized type of a discriminator, such as an addition annotation parameter as an enum of supported types, defaulting to string

[sandwwraith]

So the actual problem is that you can't use discriminators like {"type": 123}, without the quotes?

[JesseCorbett]

That is essentially the problem, yes