Add Polyglot plugin for multilingual support

[ampuEus]

Description

I am implementing Polyglot to my own chirpy blog. And I was wondering if you think it can be useful to make a pull request to implement it here as well. There are different ways to implement Polyglot and I think it's best for the community to decide how I integrate Polyglot with chirpy.

I think it is something that is being requested:

• How to let user choose between languages ? #461 - How to let user choose between languages ?
• Chirpy theme multilingual #604 - Chirpy theme multilingual
• Multiple Language #660 - Multiple Language
• Add multilanguage support (polyglot plugin) #1818 - Add multilanguage support -> A discontinued implementation

And there are already people who have it working on their own:

• https://www.yunseo.kim/
• https://aturret.space/

So if you like, I will create a pull request to deal with the issue.