[Feature] Add a search bar to quickly search for books in the website

This would be beneficial to make the website more useful to find new book. 

Similar website https://www.bigbookofr.com/ benefit from **bookdown** search feature for example.

I believe we could reuse what has been done in hugo prose
https://github.com/yihui/hugo-prose/commit/a5f32cf27e02adf45d212d28f779961f7d18d447