Add option to sleep between requests
Add option to sleep between requests

Github rate-limits POSTs to Issues and migrating too fast can lead to
being temporarily blocked like this:

403 - You have exceeded a secondary rate limit and have been
temporarily blocked from content creation. Please retry your request
again later. // See:
https://docs.github.com/rest/overview/resources-in-the-rest-api#secondary-rate-limits (Octokit::Forbidden)

johnf/github-issue-importer