Support PEP 604 unions, types.UnionType

[antonagestam]

Fixes #180

This is essentially the same fix as this one: ilevkivskyi/typing_inspect#83

[jodal]

After patching some other APIs to work with PEP 604 union types, this fix looks correct to me.

[idanmiara]

Hi @konradhalas,
Is this going to be merged for the next version?

Thanks @antonagestam

If only I spent a few minutes to check if that was already fixed before spending the time to fix it myself :( ...
#189

[anstadnik]

Hi @konradhalas, I too stumbled upon this and spent a lot of time trying to fix things.
What makes things harder is that if used in concurrent env, this error sometimes cause deadlocks, so it's easy to start searching in the wrong direction
Hope you find time to merge this PR :)

[ccwienk]

I would also love to see a new version of dacite including this fix. dacite is currently keeping us from consistently using shorthand-typehints for optional attrs in dataclasses :-(

[Sclafus]

Hello, is this pull request still active? Just encountered an issue because of the issue mentioned.

[konradhalas]

@antonagestam thank you very much for your PR - good job! I'm sorry you had to wait so long.

[antonagestam]

@konradhalas No worries, thank you for merging this. OSS is free work and I have a lot of respect for the time it takes from people's lives. So, thanks again! 🙏