Add health check to ensure Docker Swarm stops old containers after new one is healthy

nixpacks.toml

@@ -3,3 +3,9 @@ cmds = ["npm run build"]
 
 [start]
 cmd = "npx serve dist -l 80 -s"
+
+[healthcheck]
+cmd = "curl -f http://localhost:80/ || exit 1"
+interval = "10s"
+timeout = "5s"
+retries = 3