Set window title on Windows for running unpackaged

[nickrandolph]

What would you like to be added:

When running Windows target unpackaged, the title isn't being set. This needs to be read from packageappx.manifest and then set using appWindow.Title (reading packageappx.manifest can be done either at runtime, or at design time when resizetizer runs)

Why is this needed:

For which Platform:

• iOS
• Android
• WebAssembly
• WebAssembly renders for Xamarin.Forms
• Windows
• Build tasks

Anything else we need to know?