Install curl on the Docker image

[michaelfahmy]

This PR adds the curl utility to the Prometheus Exporter Docker image (ghcr.io/discourse/prometheus_exporter).

Changes Made:

• Updated the Dockerfile to install curl during the image build process.
• This ensures that the curl command is available in the container, which is critical for performing health checks (e.g., curl -sSf http://localhost:9394/ping).

[tgxworld]

• which is critical for performing health checks (e.g., curl -sSf http://localhost:9394/ping).

Wouldn't health checks be performed from an external service connecting to a port exposed by the Docker container?

[michaelfahmy]

Wouldn't health checks be performed from an external service connecting to a port exposed by the Docker container?

The image is used on AWS ECS, so I'm defining the health check for the container on the task definition, which is running on the same host.