Build warning - CSC : warning CS8784

On biulding a project created following the instaructions in the README, I recevie the following warning. The build does succeed, and produces a runable Wasm.

```
CSC : warning CS8784: Generator 'VtableIndexStubGenerator' failed to initialize. It will not contribute to the output and compilation e
rrors may occur as a result. Exception was of type 'TypeLoadException' with message 'Could not load type 'Microsoft.Interop.Marshalling
GeneratorFactoryKey`1' from assembly 'Microsoft.Interop.SourceGeneration, Version=9.0.10.30401, Culture=neutral, PublicKeyToken=b03f5f7
f11d50a3a'.'. [C:\Users\mikkelhegn\test\MyApp\MyApp.csproj]
CSC : warning CS8784: Generator 'LibraryImportGenerator' failed to initialize. It will not contribute to the output and compilation err
ors may occur as a result. Exception was of type 'TypeLoadException' with message 'Could not load type 'Microsoft.Interop.MarshallingGe
neratorFactoryKey`1' from assembly 'Microsoft.Interop.SourceGeneration, Version=9.0.10.30401, Culture=neutral, PublicKeyToken=b03f5f7f1
1d50a3a'.'. [C:\Users\mikkelhegn\test\MyApp\MyApp.csproj]
```

README の手順に従ってサンプルプロジェクトを作成し、ビルドして、VtableIndexStubGenerator と LibraryImportGenerator に対する CS8784 警告を取得します。生成された build 出力を報告された TypeLoadException と比較します。完了の条件は、プロジェクトがこれらの警告なしで引き続き実行可能な Wasm を生成することです。

索引モデルが issue の本文から書いたものです。