Critical CVEs are not exposed by the Prometheus exporter #81

Hi,

It looks like Critical CVEs are currently not exposed by the NeuVector Prometheus exporter.

The NeuVector REST API does return Critical vulnerability counts. For example, /v1/workload returns the following scan_summary for one of our workloads, e.g.:

{
"critical": 190,
"high": 1017,
"medium": 989
}

However, the Prometheus exporter only exposes the High and Medium values:

nv_container_vulnerabilityHigh 1017
nv_container_vulnerabilityMedium 989

Looking at the exporter Python code, the container vulnerability collector only handles scan['high'] and scan['medium']; there is currently no corresponding handling for scan['critical'].

The same appears to be the case for image and platform vulnerability metrics.

Are there any plans to add Critical CVE metrics to the Prometheus exporter, for example nv_container_vulnerabilityCritical (and equivalents for image/platform vulnerabilities)?