docs: update npm script to setup husky

[risu729]

Summary

Update the docs about the npm script to set up husky upon package installation.

• Use scripts.prepare instead of scripts.postinstall to follow the husky recommendation.
  https://typicode.github.io/husky/how-to.html#manual-setup

  The reason to use prepare is stated here.

  But in short, postinstall will be executed when you run npm install some-package. While prepare will run in "development" only.
  recommend postinstall instead of prepare? typicode/husky#1309

• Update the command husky install to husky which is changed in husky v9.
  https://github.com/typicode/husky/releases/tag/v9.0.1#how-to-migrate:~:text=steps%20to%20migrate%3A-,package.json,-%7B%0A%20%20%22scripts%22%3A%20%7B%0A%2D

Test Plan

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[ematipico]

Thank you!