super-high cost when searching for documents

## Reproduce

Just search from https://pekko.apache.org/docs/pekko/current//index.html

Happened on:

- m1 macOS Safari
- m1 macOS Chrome
- iPhone Safari

I think this maybe a issue from paradox.

## Self-diagnosis

Just a quick investigation from myself, the profiler shows that most of the time costs from a `reduce` function.

I am not a frontend developer, can not deep dive to it.

## Performance Profile

This is my profiler result.

[Trace-20240204T004355.json](https://github.com/apache/incubator-pekko/files/14152202/Trace-20240204T004355.json)