[Request] [zsh/en]

Its getting pretty popular with all that [oh-my-zsh](https://github.com/robbyrussell/oh-my-zsh). Since I'd like to fix and add new plugins for oh-my-zsh, and learnxinyminutes is the easiest way for me to learn new langauges, I'd like a zsh page added this website!

The issue names no file, test, or entry point. Start by locating the repository’s existing language-page structure and comparing it with the requested zsh and oh-my-zsh use case; done means a complete zsh page is added in the project’s expected format.

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