Add CLI shell completion documentation (#112)

* Add CLI shell completion documentation

* Update cli.md

Co-authored-by: Kyle Spearrin <kspearrin@users.noreply.github.com>

_articles/miscellaneous/cli.md

@@ -45,6 +45,8 @@ Bitwarden provides a powerful, full-featured command-line interface (CLI) tool t
     - [Version](#version)
 - [Working with JSON](#working-with-json)
 - [Self-signed Certificates](#self-signed-certificates)
+- [Shell Completion](#shell-completion)
+    - [ZSH](#zsh)
 - [Source Code](#source-code)
 - [Appendix](#appendix)
     - [Templates](#templates)
@@ -427,6 +429,40 @@ If your self-hosted Bitwarden server exposes as self-signed TLS certificate, spe
 
     $env:NODE_EXTRA_CA_CERTS="absolute/path/to/your/certificates.pem"
 
+
+## Shell Completion
+
+Bitwarded CLI comes with support for shell completion. It can generate shell completion scripts that you can use to enable completion for `bw` in your shell.
+
+### ZSH
+
+You can enable `bw` completion for ZSH using various methods. A few of them are mentioned below:
+
+**vanilla (.zshrc)**:
+
+Add the following line in your `.zshrc` file:
+
+```
+eval "$(bw completion --shell zsh); compdef _bw bw;"
+```
+
+**vanilla (vendor-completions)**:
+
+Run the following command:
+
+```
+bw completion --shell zsh | sudo tee /usr/share/zsh/vendor-completions/_bw
+```
+
+[**zinit**](https://github.com/zdharma/zinit):
+
+Run the following commands:
+
+```
+bw completion --shell zsh > ~/.local/share/zsh/completions/_bw
+zinit creinstall ~/.local/share/zsh/completions
+```
+
 ## Source Code
 
 As with everything here at Bitwarden, the CLI is fully open source and hosted on GitHub at <https://github.com/bitwarden/cli>.