Update Windows App SDK version to 1.8

[Avid29]

This is blocking any project depending on behaviors from updating, including the community toolkit.
CommunityToolkit/Windows#734

This is because Windows App SDK 1.6 would overwrite the CustomBeforeMicrosoftCommonTargets macro, and 1.8 introduces a check that the macro is not overwritten. As a result, Windows App SDK 1.6 and 1.8 cannot be used together.

[spadapet]

Fixed by:

• Update Microsoft.WindowsAppSDK 1.6 -> 1.8 #314

[DominicMaas]

Is there a timeline for nuget package release?

[spadapet]

@Sergio0694 do you know how the nuget packages were previously updated?

[Sergio0694]

Yeah we just kicked off the internal pipeline, let me ping you on Teams 🙂