docs: mention yarn install in setup

[MyMPublicidad]

Summary

• Add an explicit step in the Setup section to run yarn at the repository root.

Rationale

• Aligns the Setup instructions with the Getting started section and helps avoid missing dependency issues for new contributors.

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[vercel]

@MyMPublicidad is attempting to deploy a commit to the Coinbase Team on Vercel.

A member of the Team first needs to authorize it.