Integrate drand-client from this century

Currently there are a few blockers to integrating the drand js client:
- the current vuepress is very old and only supports node 16
- its bundled version of webpack doesn't have polyfills for a bunch of js features used in the js `drand-client`
- configuring the bundled version of webpack with newer babel loaders seems to fuck things up; even installing a newer version of babel spits out a wall of errors

I tried updating to vuepress 2.x (currently in RC). This works with newer versions of node, and uses a modern version of webpack but... basically everything has changed. All plugins are different and it seems like a serious effort to make it works, see: https://v2.vuepress.vuejs.org/guide/migration.html

I tried naively dropping it in and immediately had to change the config format as per [this](https://v2.vuepress.vuejs.org/guide/troubleshooting.html). Dropping in the new config format didn't work.