Serve public Grafana dashboards

Summary:
Grafana allows to share dashboards for public access.

The /public-dashboards location conflicts with the /public block.

Test Plan: Browse https://grafana.nasqueron.org/public-dashboards/34fb3078ada14509804e15b4a48d2391?orgId=1

Reviewers: DorianWinty

Reviewed By: DorianWinty

Differential Revision: https://devcentral.nasqueron.org/D3505