Upgrade web ui dependencies

[avatus]

A couple of web UI dependencies keep popping up every dependabot update that would require a bit more work than "poke around and maybe fix some new type error". We'd need to schedule some time to get these handled. This will be a living list that we can tackle separately or when it grows to a length that we think could fit into a "meta goal" for a quarter.

1. react-day-picker. see comment
   this probably could be tackled pretty quickly but requires a bit of extensive testing to ensure the styles are kept the same (or agreed upon an upgrade) around the app.

2. react-router (and react-router-dom) see comment
   not only does react router usually make breaking changes in their major version updates (makes sense) but they seem to upgrade major versions quite frequently. There are a few things that are VERY abundant in our code base (the way we use query params in our templates) that prevented us from upgrading to 6 and now they are on 7. This could be quite a large refactor but should probably be done at some point to keep us up to date.