chore: add .npmrc file

[Fdawgs]

See fastify/deepmerge#78.
This repo has a prepare script so that will just need to be ran on install when doing local development.

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[Copilot]

Pull Request Overview

This PR adds a .npmrc configuration file to prevent npm scripts from running during package installation, which is a common security practice to avoid executing untrusted code from dependencies.

• Adds .npmrc file with ignore-scripts=true setting
• Helps secure the development environment by disabling automatic script execution
• Requires manual execution of the prepare script during local development

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