Update packages / net version

[daz10000]

I'm getting the google auth example running for net6, and the newer breakdown of all the giraffe packages (at least the google auth example). Are you interested in a PR if I get a cleaned up version? (or is there a better place to start). Thanks in advance.

So far had to

• Add in open Giraffe.ViewEngine (replacing open Giraffe.GiraffeViewEngine)
• Simplified the project file a little, bumped it to net6
• Added package reference to Giraffe.ViewEngine Version="2.0.0-alpha-1

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <Compile Include="HttpsConfig.fs" />
    <Compile Include="Program.fs" />
  </ItemGroup>

  <ItemGroup>
    <PackageReference Include="Giraffe" Version="6.0.0" />
    <PackageReference Include="Giraffe.ViewEngine" Version="2.0.0-alpha-1" />
    <PackageReference Include="Microsoft.AspNetCore.Authentication.Google" Version="6.0.13"/>
  </ItemGroup>

</Project>