Once we have a UWP embedding we'll need to add support for it in the tool. We can add sub-issues for some of these once we're closer, but at a high level:

• Upload all the engine artifacts
• Add an app template
• Add a plugin template
• Add a new experiment flag
• Add new requirements to doctor, if any
• Add tool arguments for specifying UWP (and clarifying in help strings and such that the current arguments are for Win32)
• Wire up the artifact download, UWP variant build, template inflation, etc. keyed off of that argument