Publish minified files to pdfjs-dist npm package

Completed feature
https://github.com/mozilla/pdf.js/issues/5487
When "node make dist" command is run JavaScript and CSS files present
under build/dist will be minified and added to same folder.
Minified files will be named as <file_name>.min.js or
<file_name>.min.css
For minifying css files YUI compressor is needed.