switched pdfjs-dist for unpdf which works in node,browser, and cloudflare

1. switched pdfjs-dist for [unpdf ](https://github.com/unjs/unpdf) which works in node,browser, and cloudflare. 2. added test for converting to md and saving test 3. consider addding functions from https://airesearch.js.org/functions/convertPDFToHTML.html ## Problem pdfjs-dist fails to import the needed legacy dist on many env causes pain Closes [insert issue #] ## Solution switched pdfjs-dist **Features**: - Details ... **Improvements**: - Details ... **Bug Fixes**: - Details ... ## Before & After Screenshots **BEFORE**: [insert screenshot here] **AFTER**: [insert screenshot here] ## Tests _What tests should be run to confirm functionality?_ ## Deploy Notes _Notes regarding deployment of the contained body of work. These should note any new dependencies, new scripts, etc._ **New environment variables**: - `env var` : env var details **New scripts**: - `script` : script details **New dependencies**: - `dependency` : dependency details **New dev dependencies**: - `dependency` : dependency details