chore(docs): Update README.md w/ usage comments (#2507)

- Address issue #2370: Fixed the comments in the usage section

Author: cslee0034

README.md

@@ -56,10 +56,14 @@ const logger = winston.createLogger({
   defaultMeta: { service: 'user-service' },
   transports: [
     //
-    // - Write all logs with importance level of `error` or less to `error.log`
-    // - Write all logs with importance level of `info` or less to `combined.log`
+    // - Write all logs with importance level of `error` or higher to `error.log`
+    //   (i.e., error, fatal, but not other levels)
     //
     new winston.transports.File({ filename: 'error.log', level: 'error' }),
+    //
+    // - Write all logs with importance level of `info` or higher to `combined.log`
+    //   (i.e., fatal, error, warn, and info, but not trace)
+    //
     new winston.transports.File({ filename: 'combined.log' }),
   ],
 });