.NET 8 & CommunityToolkit.Mvvm for WPF demo app

[vinaghost]

• Add CommunityToolkit.Mvvm
• Add .Net 8 to targetframework

Problem:

• It seems like the progress bar didn't work, Isaw the default options don't output progress bar in console so I added

custom.Progress = true;

• Remove .net framework 4.6.2, but if you want to keep this, I can find solution