Wow, I never thought there is something like Lunr.js! In my free time, I have been working on https://ipfsearch.xyz, thinking about pivoting into a direction of search in JS, but never getting the time to do it.
Now I'm pretty sad that something like ipfsearch (most of my work was rebuilding Lunr.js) already exists.
I guess I should do more research before embarking on a side project :( Anyway, I definitely learned a lot about how search engines work...
P.S.: now, I'm noticing that Lunr can't fetch the index over the network. OK, so not all time has been lost!