feat: add lib export to use nopt in non-global mode (#116)

Author: lukekarrys

lib/debug.js

@@ -0,0 +1,6 @@
+/* istanbul ignore next */
+module.exports = process.env.DEBUG_NOPT || process.env.NOPT_DEBUG
+  ? function () {
+    console.error.apply(console, arguments)
+  }
+  : function () {}