DateTimeOffset auto-generator always generates zero offset

[cmeeren]

Just noticed (from static reading of the code) that the auto-generator seems to always generate DateTimeOffset values with zero offset:

fsharp-hedgehog-experimental/src/Hedgehog.Experimental/Gen.fs

Line 383 in 6d8719a

|> AutoGenConfig.addGenerator (Gen.dateTime dateTimeRange |> Gen.map DateTimeOffset)

If that is the case, it is probably a good idea to generate various offsets. Perhaps using Gen.dateTimeOffset?

This is not an important issue for me, and I can't prioritize making a PR right now, but I wanted to mention it since I saw it.