Promote Vitest at documentation

[mateusavila]

This is pretty simple: we should promote vitest at documentation, for a few factors:

1. vue cli runs on vite.
2. vitest runs perfect with vite
3. only the folks that uses webpack will see valid point to use jest. We have to get a little more ambition here <3

In this page, says that the jest is the easier way to use vue test utils, but recently the vue team developer amazing tools that has awesome DX. So, we need to promote vitest here. https://test-utils.vuejs.org/installation/

[cexbrayat]

Sure, feel free to open a PR to update the docs 👍