databases/promscale: import promscale-0.1.1

Promscale allows Prometheus to store data in a PostgreSQL instance using the
TimescaleDB extension. Promscale can also act directly as a
Prometheus Data Source for Grafana, or other software.

By allowing a user to use SQL, in addition to PromQL, this platform empowers
the user to ask complex analytical queries from their metrics data, and thus
extract more meaningful insights.

(tnn)