Update README GITHUB_TOKEN to DEPLOY_TOKEN

[socketopp]

gitHubToken: ${{ secrets.GITHUB_TOKEN }}

Result in

 Failed to add secret. Secret names must not start with GITHUB_.  

GITHUB_TOKEN is not a valid name so I suggest the README.md is updated. Better name would be DEPLOY_TOKEN

See more: https://github.com/github/docs/pull/12095

[WalshyDev]

GITHUB_TOKEN is actually correct per the last comment in that linked issue - https://github.com/github/docs/pull/12095#issuecomment-974285693

and the associated docs: https://docs.github.com/en/actions/security-guides/automatic-token-authentication#about-the-github_token-secret

There's no manual work needed to add this token, it's automatically available to all GitHub workflows.