@digitalcraftsman thanks for sharing the gist :)
@rdwatters, as I just commented in the gist, this solution is far from perfect... In my case the number of pages has dramatically increased and downloading the index on the client side is now an issue (here: https://doc.airvantage.net/av/).
A possibility would be to have a small nodejs webapp to serve a search API based on the same lunrjs index. But it implicates adding a server, managing the index updates and monitoring this small webapp and so on...
As we speak, I'm evaluating the integration of Google Custom Search instead of this lunrjs based solution... I know.. It's a shame :)
So far it looks good, I'm afraid of losing a bit of flexibility though. Adding the small nodejs webapp is not excluded yet.
I'll post my results in this thread soon.