Downgrade core-js to fix esm.sh build issue

[cdrini]

Closes #1205

This was a strange issue.

So core-js in commit zloirock/core-js@25e9373 changed some code from typeof global.process to typeof process. Unfortunately this resulted in some part of esm.sh when transpiling for deno to think that the node library process needed to be imported. You can see it on the first line here: https://esm.sh/v130/@internetarchive/bookreader@5.0.0-64/deno/BookReader/BookReader.js .

So for now rollback core-js to the previous version before this change was introduced. Not sure where the bug lies here ; whether this is an issue with core-js or esm.sh . But this is the quickest way for us to unblock our deploy flow to archive.org

Created an issue on core-js at least: zloirock/core-js#1277

[codecov]

Codecov Report

Merging #1207 (431c74a) into master (6e1a104) will not change coverage.
The diff coverage is n/a.

❗ Current head 431c74a differs from pull request most recent head 4e61fc3. Consider uploading reports for the commit 4e61fc3 to get more accurate results

@@           Coverage Diff           @@
##           master    #1207   +/-   ##
=======================================
  Coverage   70.18%   70.18%           
=======================================
  Files          61       61           
  Lines        5142     5142           
  Branches     1064     1064           
=======================================
  Hits         3609     3609           
  Misses       1506     1506           
  Partials       27       27           

[cdrini]

Auto-merging ; tiny change