Composer autoloader optimization

Thanks for this plugin.

I noticed the composer autoloader is making a lot of file_exist checks (1788) before loading the files, which has an impact on performance.

Would it be possible for it to be built with --classmap-authoritative instead? This will stop the file_exist checks and speed up the backend processing time.

If interested more details can be found below with benchmarks of the possible improvements:
https://github.com/WordPress/developer-blog-content/issues/468