v0.26.0 — structured logger

A small leveled logger — structured JSON by default, pretty in debug:

logger().info("user registered", { userId: user.id });
logger().error("payment failed", { orderId, error });

const log = logger().child({ requestId });  // bound on every line

Levels debug < info < warn < error with a threshold from config('logger.level'). See docs/logger.md.