Add support to fail on certain conditions.

[davidlehn]

External comment:

Add /something/ so that this happens during an image build (it's something we can pull in on image build) and that will halt on crit/high vulns being found

[davidlehn]

I think the request here is to add support so the scanning action here can be used as part of a image artifact build process where policy would be strict on acceptable scan results.

I think this is doable in a controlled way by adding parameters that would control this action failing on certain types of results. Right now it'll add reports to PRs and create/update a issue for the main branch. But it could be an option for the action to fail instead. Depending on the calling codes policy, it might need some options on what type of issues are failure conditions. Like only high/critical, but others are fine.

See also the overrides issue:
#41