Allow to fail CI on scan findings #31

Hi, thank you for the package.

I was surprised to learn that slop-scan scan . --lint exits with code 0 even when it finds issues.

I added it to CI assuming findings would fail the job, so CI had been happily allowing slop through. I only noticed when I ran it locally and actually read the output.

README suggest this

slop-scan scan . --json | jq -e '.summary.findingCount == 0'

But that only prints true / false instead of the full list of findings. A native option would be much clearer:

slop-scan scan . --lint --fail-on-findings

Suggested implementation in src/cli.ts after rendering:

return args.failOnFindings && result.summary.findingCount > 0 ? 1 : 0;