docs: update installation section

docs/installation.md

@@ -5,8 +5,17 @@ title: Installation
 
 It uses [Graphviz](https://www.graphviz.org/) to render the diagram, so you need to [install Graphviz](https://graphviz.gitlab.io/download/) to use **diagrams**. After installing graphviz (or already have it), install the **diagrams**.
 
+> macOS users can download the Graphviz via `brew install graphviz` if you're using [Homebrew](https://brew.sh).
+
 ```shell
+# using pip (pip3)
 $ pip install diagrams
+
+# using pipenv
+$ pipenv install diagrams
+
+# using poetry
+$ poetry add diagrams
 ```
 
 ## Quick Start