Add rate limiting retry middleware

It would be helpful if the client creator provided an option to enable delays and retries in case of rate limiting. This should be optional because GitHub's hourly buckets mean you might have to wait a long time to try again. This also implies there should be an option for a maximum wait time, so if the retry header is past this value, the request can fail immediately. I expect this will be most useful if accidentally hitting the abuse limits (where the wait time is probably minutes), but could also be useful for regular limits.

Start by locating the client creator and the request middleware or entry point that handles GitHub responses. Trace how rate-limit and retry headers are exposed, then define the optional delay/retry behavior and maximum-wait failure case. Done means existing requests remain unchanged unless enabled, and waits beyond the configured maximum fail immediately.