Add support for `xunit.v3`

[meenzen]

Description

xUnit V3 has been released on 2024-12-16. Release announcement: https://xunit.net/releases/v3/1.0.0

[CaptnCodr]

Hi @meenzen,
I will tackle this soon. Thank you for referencing.

[CaptnCodr]

Hey @meenzen,
xunit.v3 is now part of FsUnit.Xunit 7.0 and has been released already.

Happy holidays! 🎅🏻