Readme Build Guidline Update

[Vivek09Chahal]

PR #23521 (Nov 2024) and PR #23675 switched WP.com sign-in to a web-based ASWebAuthenticationSession flow, which does require a matching redirect_uri — the custom scheme like wpdebug://oauth2-callback.

README.md still says redirect URLs are https://localhost and "required but not used for the mobile apps."

[dangermattic]

Thanks for reporting! 👍