Update frontend dependencies and related issues

[monocle]

This is a general discussion related to updating the React app. This fork's default branch is update-frontend-deps. I have push the first commit that updated most of the important dependencies 1a38954

npm audit will show a warning on nth-check, but that's okay:
facebook/create-react-app#11174
facebook/create-react-app#11647

After getting npm run start to work, there were a bunch of TypeScript warnings that needed fixing. (I have yet to learn TypeScript but am slowly muddled along fixing things.) There are some lingering issues related to upgrading dependencies:

• @reach/disclosure is no longer maintained. I forced installed this and it seems to work, but long term, maybe we should either find a replacement or just create a custom Disclosure component. Vendored.

• I did not update react-router-dom because of major API changes that broke RecordSponge. I haven't tested to see if there are issues keeping the old version with the other upgrades but this should probably get upgraded regardless. Upgraded.

• The moment.js people recommend using something else. So we probably should migrate to another library or just write something custom.

I also noticed some other smaller content issues (typos, broken link, etc) that could get opened on the main repo.

There is also a larger bug that already has an issue and might take more time.