feat: ability to provision alerts for prometheus/grafana

[gustavovalverde]

Add a similar option as the one that exists for Grafana

grafana_params:
  additional_dashboards: []

But to allow provisioning alert rules

[parithosh]

Would you envision the config to just accept a raw JSON file hosted as a gist or something and for grafana to import it?

[savageyoongi]

I'd like to take this issue. I'll start working on it.