Fix MSIX bundle crashes when publishing with trimming enabled

[Copilot]

Issue

When publishing a .NET application as an MSIX bundle with trimming enabled (PublishTrimmed=true), the application crashes with a MissingMethodException stating that System.Environment.SetEnvironmentVariable method could not be found. This occurs because the .NET trimmer removes this method, which is used by the Windows App SDK initialization code.

Changes

1. Modified UndockedRegFreeWinRT-AutoInitializer.cs to handle the case when Environment.SetEnvironmentVariable is trimmed away:

   • Added a try-catch block around the method call
   • Added a fallback mechanism using AppContext.SetData which is less likely to be trimmed

2. Added documentation in the FAQ to explain the issue and solution:

   • Added a new entry explaining how to handle trimmed MSIX bundles
   • Provided alternative configuration options for those using older SDK versions

Testing

The changes have been designed to handle both scenarios:

• Normal execution path (when Environment.SetEnvironmentVariable is available)
• Trimmed application path (using AppContext.SetData as fallback)

These changes maintain backward compatibility while adding support for trimmed applications.

Fixes #1.

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