build: add a healthcheck

Author: wescopeland

Dockerfile

@@ -25,5 +25,9 @@ RUN npm run build
 # Expose port
 EXPOSE 8080
 
+# Add healthcheck to monitor app status.
+HEALTHCHECK --interval=30s --timeout=3s --start-period=45s --retries=3 \
+  CMD node -e "require('http').get('http://localhost:8080', (res) => { process.exit(res.statusCode === 200 ? 0 : 1); })"
+
 # Start the server
 CMD ["npm", "start"]