The Github iCalendar feed has now been updated to scan issues in all of your repositories.

It is no longer necessary to list your repositories in the configuration file or remember to add new repositories to the configuration from time to time.

Screenshot

Below is a screenshot from Mozilla Lightning (known as Iceowl extension on Debian) showing the issues from a range of my projects on Github.

Notice in the bottom left corner that I can switch each of my feeds on and off just by (un)ticking a box.