Changes not suppressed when switching to Uno / WinUI 3

[Arlodotexe]

Background

In https://github.com/CommunityToolkit/Labs-Windows/pull/75, we added a UseUnoWinUI.ps1 script to facilitate switching between Uno.UI and Uno.WinUI.

In #1, we moved this script into a submodule.

Problem

After the move to a submodule, switching to WinUI 3 leaves changed files in the working tree when it didn't before.

This alone isn't an issue since the script-altered files won't get committed alongside the user's normal changes.

However, changing these files causes the parent repo to update the submodule commit hash, which can easily be committed alongside normal changes:

Solution

Suppress changes to these files again so the user cannot commit them without explicitly passing the -allowGitChanges flag.