Add an option to exclude a list of packages while exporting to a file

Description of the new feature/enhancement

At it's current state, winget exports "all" packages installed on the local system & the ones which are available on a remote source to a JSON file. And there's no way to control or fine-tune what get's included in the exported JSON file.

If I had installed a software earlier just to try it out, even that get's exported to the JSON file. So, I think it would be a nice feature to have if it was possible to control & fine-tune winget's export command.

Proposed technical implementation details (optional)

Add an optional flag to the export command which would accept a list of already installed packages to exclude from the JSON file.

Of course there could be a better way to deal with it & look forward to how things turn out to be with this feature.

Start at the winget export command and trace how installed packages are selected and written to the JSON file. Define how the optional package list is supplied and matched, then verify that listed installed packages are absent while other exported packages remain unchanged.