Chrome Extension: How do I poll RSS Feeds to see if there is new content and display that as a number on the extension icon

Question

I wonder if you could help a little.

I want to have a simple Extension, that shows the number of new items in a RSS feed since the extension was clicked.

It would poll every 2-3 mins for example and if the RSS feed is updated it should display a count of how many new items there are. I assume it has to set the setBadgeText field.

Any help would be greatly appreciated.