How do health checks in Varnish help prevent 54113 errors, and how can I configure them?

Health checks periodically probe your backend servers to ensure they are responsive. If a backend fails a health check, Varnish will temporarily stop sending traffic to it, preventing 54113 errors for users. Configure health checks using the `probe` directive within the `director` section of your VCL. You can specify the URL to probe, the interval, and the timeout. Example: `probe mybackend /healthcheck -q 5s`.