Model architecture: Enable eslint for .ts files

[kring]

[kring]

microsoft/TypeScript#30553
https://github.com/typescript-eslint/typescript-eslint

[tephenavies]

Our current eslint config is really outdated. Now prettier fills a lot of the requirements we used eslint for. We should maybe consider cutting it down a lot, starting with something like:

{
  "extends": [
    "eslint:recommended",
    "prettier"
  ]
}

And add config to make it work with TypeScript etc.

We'll probably need some react rules too, e.g. see #4565.

[soyarsauce]

Related #4519 & #4565