[feature request] make tracker statistics available via prometheus

[ldpr]

Currently the tracker stats are output in json, it'd be pretty neat if we could have them available via prometheus so we could hook them into things like grafana etc.

https://docs.rs/prometheus_exporter/latest/prometheus_exporter/

Maybe we could have a config option for json or prometheus?

Obviously this isn't important or anything, would be a "nice to have". Thanks for everything you do guys and girls! :)