Stop using deprecated module.parent

Fixes: https://gitlab.com/autokent/pdf-parse/-/issues/15
Refs: nodejs/node#32217

Author: aduh95

index.js

@@ -3,7 +3,7 @@ const Pdf = require('./lib/pdf-parse.js');
 
 module.exports = Pdf;
 
-let isDebugMode = !module.parent; 
+let isDebugMode = require.main === module; 
 
 //process.env.AUTO_KENT_DEBUG