Handle 429 status code with retry

[KingAkeem]

429 indicates too many requests and possibly has a header attached that indicates when another request should be retried Retry-After.

This could be used to pull those requests into a separate "retry" channel that will retry those requests after the Retry-After period has passed or a default time period. This would help to eliminate false negatives for sites that are actually up and running.

https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/429 https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Retry-After