Add detection for zsh completion files

[griano]

Chenges

• In ZSH completions files start with #compdef and #autoload, like these files

• I also added detection for some typical ZSH env files.

  Testing

• rake passes all tests

• Example with #autoload

  $ ./bin/rougify guess =(curl -sq https://github.com/zsh-users/zsh/blob/master/Completion/Base/Utility/_arguments)
  { tag: "html", title: "HTML", desc: "HTML, the markup language of the web" }

• Example with #compdef

  $ ./bin/rougify guess =(curl -sq https://github.com/zsh-users/zsh/blob/master/Completion/Zsh/Command/_alias)                                                                               
  { tag: "html", title: "HTML", desc: "HTML, the markup language of the web" }

[tancnle]

Thank you for considering the suggestions, @griano. The change LGTM 🚀

[griano]

Addressed the requested changes.

Testing:

The test above were reported incorrectly. In these tests I use the raw URL to download the actual file.

Test with #autoload

$ bin/rougify guess <(curl -sq https://raw.githubusercontent.com/zsh-users/zsh/master/Completion/Base/Utility/_arguments) 
{ tag: "shell", title: "shell", desc: "Various shell languages, including sh and bash" }

Test with `#compdef``

$ bin/rougify guess <(curl -qs https://raw.githubusercontent.com/zsh-users/zsh/master/Completion/Zsh/Command/_alias)
{ tag: "shell", title: "shell", desc: "Various shell languages, including sh and bash" }
```bash