update for v3 pdf.js

[sterlingwes]

I needed a fix for RTL language support in pdf.js and found some issues pulling in a more recent version:

• v4 made some big refactors around ESM modules and typescript that led the team to remove a module we're depending on (domstubs.js)
• v3 had better support for the existing project structure with some minor tweaks:
  • new gulp dist path
  • promise not returned by getDocument call, now a "task" class wrapper with promise getter

I've updated the readme to make it clear what version of PDF.js is supported with these changes, since it seems that V4 will require a fairly significant overhaul

RE: the global require "hacks", I'm not sure how it worked before, but the existing require calls in parse-cmd were not making pdfjsLib available so i added an explicit require call to pdf-table-extractor.js. This tells me that the require for domstubs might not be necessary but I didn't check that since the code as-is works for my needs.

[HiiiXinyiii]

Highly recommend this PR. Thank you!

The referred project pdf.js has been updated. This PR has pointed out the right version and solved the related running issues.