[zipSync] To migrate from JSZip to fflate, there are incompatibilities found.

[cyfung1031]

1. adding comment field for the entire zip file is not available - see Adding comment field to the whole zip rather than per-file #269
2. compression of >655,35 files is not available - see zip does not support >65,535 files #229 Add Zip64 write support #230 Add ZIP64 footer support for archives with more than 65,535 files #270

jszip-limit-test.html
fflate-zipsync-limit-test.html