Upgrade TypeScript and other minor JS dependencies

[lemald]

Asana ticket: ⚙️ Upgrade TypeScript to 4.x

Most of the TypeScript upgrade itself was pretty straightforward. A couple of minor notes:

• We had been using an argument to reload. This is apparently only supported on Firefox and even then doesn't really do anything for our purposes (if there's a new version of the app, the fact that we're using mix phx.digest means the static assets will be at a different URL anyway). The types were causing issues so I went ahead and just removed the parameter.
• The resize-observer-polyfill package also had some issues, see here. However, from discussion with my PM we agreed to drop support for older browsers that don't have native ResizeObserver support (which would be pretty out-of-date at this point anyway). If this becomes an issue we can also use @juggle/resize-observer, which seems better supported.
• I also upgraded a handful of other JS dependencies that looked like low-hanging fruit.

[github-actions]

Coverage of commit f625aa3

Summary coverage rate:
  lines......: 94.8% (2314 of 2441 lines)
  functions..: 69.8% (997 of 1429 functions)
  branches...: no data found

Files changed coverage rate: n/a

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[boringcactus]

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