[Feature] Update to EF Core 6

[tonysneed]

Update to EF Core 6 sometime before EF Core 6 is released.

[tibitoth]

@tonysneed EF Core 6 was released :)

[tonysneed]

Hi folks, Super sorry I haven’t been able to upgrade for EF Core 6 in time. It will be my top priority this weekend.

Of course, a PR would be gratefully accepted!

[biesterv]

Nice work Rich!

[tonysneed]

Closed by #190. Thank you Rich!

[tonysneed]

Upgrade included with release v6.0.0-preview1.

NuGet: https://www.nuget.org/packages/EntityFrameworkCore.Scaffolding.Handlebars/6.0.0-preview1