Upgrade to more recent version of xlsx package

[chrispcampbell]

We are currently using v0.17.5 of the xlsx (aka SheetJS) package. That package has had a few security alerts in the past couple years, the latest one says to upgrade to v0.20.2. One hitch is that the SheetJS maintainers have been in a battle with npmjs for a while and no longer publish their packages to the npm registry, so their instructions now say to install from their own CDN:

    "xlsx": "https://cdn.sheetjs.com/xlsx-0.20.2/xlsx-0.20.2.tgz"

I'm not a fan of relying on a self-hosted binary (which they could take down at any time), and I'm not a fan of their development approach, but unfortunately there are no easy alternatives at this time. The other ones I looked into, exceljs and read-excel-file, only support async reading of files, so even if I wanted to try them, I'd have to change a lot of compiler functions (on the code gen side) to be async ready, which is not a quick task. So for now, I'm afraid the best solution is to point to the most recent version of their self-hosted binary.

(I would still like to replace this dependency someday, maybe as part of changing the compiler to read/cache the xlsx/csv data in an earlier step rather than waiting till the code gen phase.)