Option to not sign container contents

[zooba]

Is your feature request related to a problem? Please describe.
I have a complex build where I produce one set of binaries and multiple containers. I want all the binaries to be signed once so they are identical in each container. This tool always signs the contents of my Nuget and MSIX containers, even though they are already signed.

Describe the solution you'd like
A command line option to only sign the specified container itself, and not extract it and sign every file inside of it.

Updating the appxmanifest is nice, though, but I'd happily provide a second option to do that. My build already handles updating it manually.

Describe alternatives you've considered
An environment variable would also be fine.

Additional context
Include the output of sign --version.

0.9.1-beta.24469.1+5516908609085978174904945d54144c117041dc

(On my local machine, not my CI machine, but it's installed fresh every time there. I'm not running an official build to get a version number for a feature request - I've already checked that there's no code in main that would do what I need.)

[dlemstra]

This sounds like a reasonable addition but this should probably be an option instead of a check for an environment variable.