draft: establish a clean tsconfig.json

[imkesin]

Task

Use npm run typecheck or npx tsc --noEmit to figure out where there are type errors in the repo.

A significant chunk of them are related to noUncheckedIndexAccess.

I encourage you to use type guards when possible:

type ArrayWithAtLeastTwo<T> = readonly [T, T, ...T[]]

export function isArrayWithAtLeastTwo<T>(list: ReadonlyArray<T>): list is ArrayWithAtLeastTwo<T> {
  return list.length >= 2
}

[imkesin]

These two need to be addressed in a follow-on PR.

They mostly related to the usage of import type syntax.

[imkesin]

This has been superceded by #625