Clear and concise description of the problem

I'm trying to migrate from uvu to vitest and noticed that there's no assert.unreachable

Suggested solution

https://github.com/lukeed/uvu/blob/56e1cb25ecd76cbf5cd3fd28c7a4c07db405c5c3/src/assert.js#L48

Alternative

Just do throw new Error();. Feel free to close this issue if that's preferred

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.