Need to support conditional packagereferences

[mrlacey]

#35 is for a package that doesn't support net8.0 and so can't be referenced in a package that also includes the test project.

Can work around this by setting: <PackageReference Include="Plugin.MauiMTAdmob" Version="1.1.1" Condition="'$(TargetFramework)' != 'net8.0'" />

However, the current generator code doesn't support setting a condition for a package added via the add Nuget package postaction.
Look at modifying/extending the postaction, or adding a new postaction that can run afterwards and set the condition.

[mrlacey]

Also need this to support DebugRainbows https://www.nuget.org/packages/Plugin.Maui.DebugRainbows#supportedframeworks-body-tab