Add alerting configurations

Add traefik_rules.yml

Add scrape config to fetch traefik metrics

Add pending evaluations nomad rule

Add unack evals nomad rules

Add nomad_rules.yml

Use raw artifact from sr.ht rather than github

Add prometheus configuration files

Nomad configurations for promteheus, alert-manager, and node-exporter,
as well as Prometheus alerting rules for nodes, and the Prometheus main
config file.