Add znap

[rossmacarthur]

See https://github.com/marlonrichert/zsh-snap

[marlonrichert]

Some notes about Znap:

• If install time is a concern, you can use znap clone to download plugins in parallel. For example, you can add this at the top of your .zshrc file or just run it once on the command line:

  znap clone \
    marlonrichert/{zcolors,zsh-autocomplete,zsh-edit,zsh-hist} \
    zsh-user/{zsh-autosuggestions,zsh-completions,zsh-syntax-highlighting}

  If a plugin is already there, then znap clone will silently ignore it and not download it again.

• When znap prompt is executed, your prompt becomes visible instantly, even while the rest of your .zshrc hasn't loaded yet. For example:

  source ~/Git/zsh-snap/znap.zsh
  
  znap prompt sindresorhus/pure  # Prompt becomes visible _immediately_ at this point.
  
  # Everything below happens while you are already typing at the prompt.
  znap source marlonrichert/zsh-autocomplete
  znap source zsh-users/zsh-autosuggestions
  znap source zsh-users/zsh-syntax-highlighting

  This way, it matters far less how long the rest of your .zshrc takes to execute. Since your prompt is there and you're able to type, it feels like your shell has already finished starting up. If you're going to measure load time, you should also measure time-to-prompt.

• Nearly all users do more in their dotfiles than just source Zsh plugins. For example, they might have expensive eval statements in their .zshrc, like this one:

  eval "$( pipenv --completion )"

  This particular statement can take up to 0.5 seconds to execute. However, you can speed that up considerably by using znap eval:

  znap eval pipenv-completion 'pipenv --completion'

  Now it takes only 2 milliseconds! If you really want to measure performance, then you should also include eval statements, since these are typically what takes the most time in one's .zshrc file.