Feature request: Ability to sign nupkg and snupkg in one step

[MichaelGrafnetter]

Hi, first of all, thanks for this great tool.
I stumbled upon a minor issue that although the tool supports wildcards (e.g. Packages/*.nupkg or Packages/*.snupkg), it is unwilling to sign both *.nupkg and *.snupkg files at the same time (Packages/*.* or Packages/*nupkg), it will only sign *.nupkg ones. This means that CI pipelines need to call the NuGetKeyVaultSignTool twice instead of once, with a ton of parameters 😉.