Currently Ava is used to unit test the api/node project.
Vitest is already used elsewhere in the monorepo, integrates well with
Vite, is fast and automatically handles tests written in Typescript.
Replacing Ava would simplify how Typescript tests are performed.
This PR introduces Vitest to the project, sets it up to match Ava
(isolated process for each test) and ports just the window.spec.mts
file.
Later PR's will port the rest.