This PR makes all packages share the same typescript version and updates us to
latest versions of typescript, ts-node, typescript-eslint/eslint-plugin and
typescript-eslint/parser.
I also noticed that the tsconfig we were extending (node18-strictest) was
deprecated, so I switched us over to one that's more up to date.
Also had to make a couple of small changes to the playground so that continues
to build correctly.