[Feature] Use Jekyll Simple Search

[Andrew-Chen-Wang]

You can simply implement Jekyll simple search with a CDN (e.g. cdnjs) and inline JS to activate.

You should probably use an animation from here: https://freefrontend.com/css-search-boxes/

Additionally, it's recommended to also have an actual button with a search page to show results in case users want an engaging feature like a search button (especially mobile design since they can't see the result list).