[Feature]: Prometheus integration

What is the installation method of your PatchMon server?

Docker

What is the version of your PatchMon server?

1.4.2

Briefly describe the feature

Add a prometheus (OpenMetrics) exporter/metrics endpoint

Detailed description

A Prometheus metrics path or exporter for PatchMon which would allow for exporting the metrics (eg. # of outdated hosts, host OS distribution, any metric PatchMon collects, really) to a Prometheus instance.

Why is this useful?

In my stack, I run Prometheus and Grafana for monitoring. Having everything integrated into a pre-existing tool would allow for better observability and manageability, which is the point of PatchMon. While the existing user interface is convenient and easy to understand, having the flexibility to view the data somewhere else would be quite useful especially in an enterprise setting where PatchMon is becoming more likely to be considered by administrators.
Furthermore, this would allow for more security, by for example not having PatchMon exposed to the Internet (or exposed via reverse proxy), but silently sending metrics to Prometheus and Grafana which, having more maturity, are more likely to be trusted by professionals. While I'm sure PatchMon's secutiry is competent, not exposing a service like it would be better overall.
Additionally, the rewrite in Go is quite convenient as Prometheus and most exporters are written in Go and Prometheus provides examples on how to write exporters in Go.

Thank you!