Having a domain name and website for your project is great. You don't want #GitHub to own the entire online identity of your project.
But you should stay away from the .io TLD:
1. It's a country TLD that's disputed, and while it may not go anywhere…
2. It's getting more and more expensive, which for #FOSS projects is a problem.
The best TLD for FOSS projects is probably the .org TLD.
Or, if stuck on .io, at least pre-pay it for years in advance.