feat: add `fastify install` command

[matthyk]

First draft for a new fastify-cli command called install. This command can be used for any existing Fastify project to browse and install Fastify core plugins. Usage is as follows:

• fastify install my-project: Launches an interactive CLI powered by Inquirer.js and the selected plugins will be installed in the folder my-project. A package.json must already exist in this folder.
• fastify install my-project --search sql: The CLI searches for any core plugin matching the given word and let the user select from the found plugins
• fastify help install shows:

  
  Usage: fastify install <FOLDER>

Launches an interactive CLI application that allows you to browse and install Fastify plugins. Requires an existing package.json file in the specified folder.

OPTS

--search, -s search for plugins containing the given word

TODO's:
* [ ] Add tests
* [ ] update documentation
* [ ] Optimize search functionality

#### Checklist

- [x] run `npm run test` and `npm run benchmark`
- [ ] tests and/or benchmarks are included
- [ ] documentation is changed or added
- [x] commit message and code follows the [Developer's Certification of Origin](https://github.com/fastify/.github/blob/master/CONTRIBUTING.md#developers-certificate-of-origin-11)
      and the [Code of conduct](https://github.com/fastify/.github/blob/master/CODE_OF_CONDUCT.md)

[matthyk]

@mcollina Is this approach feasible? Some points that still need to be clarified for me:

• We have to use Inquirer version 8.x since later versions are ESM modules
• Currently, the versions of the plugins are controlled via the devDependencies in package.json. I am open to other/better approaches

[mcollina]

use the latest version and switch the CLI to esm, there is no real need for the CLI to be CJS.