Add algolia search

[rewired-gh]

Algolia search is a function provided by theme.

[SoraShu]

I don't think 'weekly' needs a search function. And algolia offers limited search capabilities.

We can just turn on the archive page and pin it on the top.

[rewired-gh]

Just in case.

Also a search bar can make the web page less boring.

[Origami404]

I don't think it's necessary. People could just clone this repo and use any tool (such as VSC) they want to search over all the articles -- or even use Github's code server (just press the . in repo frontpage).