Feature: Support for WinUI3 desktop

[harvinders]

What kind of change does this PR introduce?

It adds support for WinUI 3 desktop. Will add more information as I proceed further.

What is the current behavior?

What is the new behavior?

What might this PR break?

Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Other information:

[dnfadmin]

All CLA requirements met.

[glennawatson]

We will merge your PR then add support for net6 version as well.

Thanks for your help.

[kmgallahan]

@harvinders When I install the ReactiveUI.WinUI package I receive this error:

This is with a blank WinUI 3 desktop app created using the Windows App SDK 1.0.0-preview1 template (with no page declarations in the project files).

[harvinders]

It is maybe because Microsoft has decided to rename the nuget package from Microsoft.ProjectReunion to Microsoft.WindowsAppSDK in preview 1.

ReactiveUI.WinUI package would need to be complied with final released version 1.0 to fix it.

[glennawatson]

This is why we normally never support anything that hasn't had a full release.

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.