It's time to update this app for WinUI3

[gmgallo]

There are a number of new controls in WinUI 3 that are not included in this app. To make it future proof and really useful I would add this two things to the wish list:

1. Allow the user to import new controls besides the fix set of built in common controls.
2. I import actual style definitions to edit and save again
   Just my two cents.