Handle rate limiting from GitHub API

[mattprecious]

https://docs.github.com/en/rest/overview/resources-in-the-rest-api?apiVersion=2022-11-28#secondary-rate-limits
https://docs.github.com/en/rest/guides/best-practices-for-integrators?apiVersion=2022-11-28#dealing-with-rate-limits

I think "handle" here just means: detect this and output a better message. There's not much we can really do about it since all our operations are manually triggered and not issued by some service.

The GitHub library we're using has top-level functionality for checking and handling rate limits:

• https://github-api.kohsuke.org/apidocs/org/kohsuke/github/GitHubBuilder.html#withRateLimitChecker(org.kohsuke.github.RateLimitChecker)
• https://github-api.kohsuke.org/apidocs/org/kohsuke/github/GitHubBuilder.html#withRateLimitHandler(org.kohsuke.github.GitHubRateLimitHandler)