Feature request: Limit backup to open issues and PRs, or starting at a certain date or id #514

What would you like to happen?

• An option to only backup any issues and PRs that are still open
• An option to only backup issues and PRs starting at a specific id number or date

Would be very useful for larger repositories, where a fully backup might take several days because of API throttling.
In most cases the open issues and PRs are the most relevant for future work.