feat: make Vite configuration available from distribution bundle

[onlywei]

Addresses #155

Adds a new config option that needs a vite plugin to work.

By default, @fastify/vite looks up the Vite configuration options by importing Vite from node_modules and then using its Node API to look up the vite.config file. This is often not desirable in production mode since many production builds declare Vite as a devDependency and exclude it from their final container/docker images to save space.

To support this kind of production build, this PR makes @fastify/vite ship with a Vite plugin that can save the handful of properties that it needs from the resolved Vite configuration object to a file in your dist directory. These properties can than be loaded instead of loading the config through vite itself.

See the changes to the docs/config/index.md file for exactly what is happening in this change.

Checklist

• [x] run npm run test and npm run benchmark
• [x] tests and/or benchmarks are included
• [x] documentation is changed or added
• [x] commit message and code follows the Developer's Certification of Origin and the Code of conduct

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[galvez]

This is absolutely amazing, thank you @onlywei! I'll be reviewing shortly.