Vitest port

Hi @Lusito, you didn't have discussions enabled so I'm opening an issue instead.

Just wanted to let you know I made a best-effort port of mockzilla to Vitest as the webextension mocking functionality implemented here is the best I've seen and I wanted to use it with Vite plugins like [`unplugin-auto-import`](https://github.com/antfu/unplugin-auto-import).

I only modified the code and docs where it was necessary to make it compatible with Vitest, and restructured the project to use a monorepo structure.

I've licensed all of my modifications under the same license as Mockzilla itself and linked to this repo from the top-level `README.md`, I hope that's enough.

If you have any requests, complaints, issues or nitpicks regarding copyright/licensing/attribution etc. then I'll gladly help resolve them.

Lastly - if there's any piece of code you can think of that's obviously jest-specific (the error reporting functionality comes to mind here, I have yet to test it) it'd be nice to know.

Thanks for making this!

EDIT: forgot to link to the actual project: https://github.com/ohmree/vitezilla

Review the linked vitezilla project and the top-level README to understand the proposed Vitest port and monorepo restructuring. Then inspect the existing error-reporting functionality for Jest-specific behavior. Done means deciding whether the port belongs in Mockzilla and documenting or addressing any compatibility concerns.

Written by the indexing model from the issue text.