docs(ecosystem): add lint tip for ecosystem.json

[EduconPC133]

Summary

Add a short tip under the ecosystem.json instructions explaining how to run yarn lint:ecosystem to validate entries before opening a PR.

Motivation

This helps contributors catch missing fields, invalid category/subcategory values, and JSON formatting issues earlier in the workflow.

[vercel]

@EduconPC133 is attempting to deploy a commit to the Coinbase Team on Vercel.

A member of the Team first needs to authorize it.

[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