Support PEP 604 union annotations

[dnnsthnnr]

What was changed

Added support for 3.10 / PEP 604 union annotations in the format of int | str.

Why?

Closes #255

Checklist

1. Closes [Bug] PEP 604 style optionals not working properly #255

2. How was this tested:
   Tests for the JSON converter for the PEP 604 annotations have been added and the tests actions passed on my clones repository for 3.11 and 3.7

3. Any docs updates needed?

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[cretz]

Thanks! If/when CI completes, I'll merge.