refactor: make decode non-enumerable

see #741

index.js

@@ -1,8 +1,12 @@
 module.exports = {
-  decode: require('./decode'),
   verify: require('./verify'),
   sign: require('./sign'),
   JsonWebTokenError: require('./lib/JsonWebTokenError'),
   NotBeforeError: require('./lib/NotBeforeError'),
   TokenExpiredError: require('./lib/TokenExpiredError'),
 };
+
+Object.defineProperty(module.exports, 'decode', {
+  enumerable: false,
+  value: require('./decode'),
+});