Allow ordering by popularity

[Tim Carry]

As I have a lot of records, I don't want to duplicate them in a replica. I think there is now the ability to do it without replicating.

https://www.algolia.com/doc/guides/managing-results/refine-results/sorting/in-depth/replicas/

Seems like I'll need to use a virtual replica; still need to see if it works with a keyword