[Windows] Support standalone executables

[tuzz]

Hello, thanks for a great tool.

I'm using cargo bundle on macOS to successfully build an .app bundle.

On Windows, it errors when creating the msi bundle (this is already recorded as an issue).

However, my app doesn't really need to be an installer. It's just a simple executable and I was hoping to use cargo bundle to set the icon and metadata so that it can be run as an .exe file directly.

At the moment, I can do this with the winres crate. However, that requires a different set of config that has to be kept in-sync with cargo bundle's config. It also requires a small build script to set the icon and it doesn't support converting from a png, etc.

I was wondering whether it would be possible to roll this functionality into cargo bundle so it's just another --format it supports? That way, many of the people running into the msi problem could use this approach instead if their app is simple enough.

Thanks