update everything; fix all vulnerabilities; switch to pnpm

[williamstein]

I don't know if anybody but me is worried about maintaining this package. In my own version on npm @cocalc/ansi-to-react, I did update everything, fix all the security vulnerabilities, etc. The tests still pass and this works for me for cocalc.

Here's a PR to do it. If anybody is out there, I can merge it, but I don't think I can push to your npm repo.