Make it clearer that the project uses `yarn` rather than `npm`

Hello,
It is my first time working with npm and I was trying to install the correct packages in order to work on this issue: https://github.com/code-chronicles-code/leetcode-curriculum/issues/305

but I kept on getting this error

However, I was able to resolve it by changing all the eslint versions to "^8". Did you face a similar issue by any chance?

Review the installation context described here and the linked issue #305, then locate where the project currently explains its package-manager workflow. Make the Yarn requirement unambiguous and verify that the documented installation path avoids the reported npm and ESLint confusion.

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