Get start with FsCheck and FsCheck.Xunit

ref link:[NuGet Gallery

FsCheck 2.15.3](https://www.nuget.org/packages/FsCheck)

[NuGet Gallery

FsCheck.Xunit 3.0.0-alpha5](https://www.nuget.org/packages/FsCheck.Xunit/3.0.0-alpha5)