CommonJs Dependancy jszip

Getting warnings when using in angular project: /node_modules/read-excel-file/modules/read/unpackXlsxFileBrowser.js depends on 'jszip'. CommonJS or AMD dependencies can cause optimization bailouts.

In an open issue on jszip it is suggested to use fflate instead as it is faster, supports ES modules, and smaller. https://github.com/Stuk/jszip/issues/717