Required PDF.js library is not installed when using composer

This issue and https://www.drupal.org/project/pdf/issues/3365327 📌 Use composer to handle the dependency on pdf.js Active seem to addressing the same problem. Perhaps the solution it that issue can be implemented.

For those that ended up here for the reason I did, the instructions for #15 worked and in on par with usual practices.

albert volkman → made their first commit to this issue’s fork.