Documented graphviz install

Author: chriscarrollsmith

README.md

@@ -23,13 +23,30 @@ disadvantage is that it requires an extra round trip to the database to
 fetch the updated data, and re-rendering the entire page template may be
 less efficient than a partial page update on the client side.
 
-### Install development dependencies
+### Install development dependencies in a VSCode Dev Container
+
+If you use VSCode with Docker, the following VSCode Dev Container configuration will install all dependencies and automatically open the project in a container:
+
+``` json
+{
+	"name": "Python 3",
+	"image": "mcr.microsoft.com/devcontainers/python:1-3.12-bullseye",
+	"postCreateCommand": "sudo apt update && sudo apt install -y python3-dev libpq-dev graphviz && pipx install poetry && poetry install && poetry shell",
+	"features": {
+		"ghcr.io/devcontainers/features/docker-outside-of-docker:1": {},
+		"ghcr.io/rocker-org/devcontainer-features/quarto-cli:1": {}
+	}
+}
+```
+
+Simply create a .devcontainer folder in the root of the project and add a devcontainer.json file with this content, and then "Reopen in Container" from View > Command Palette.
+
+### Install development dependencies manually
 
-#### Python, Docker, and Quarto CLI
+#### Python and Docker
 
 - [Python 3.12 or higher](https://www.python.org/downloads/)
 - [Docker and Docker Compose](https://docs.docker.com/get-docker/)
-- [Quarto CLI](https://quarto.org/docs/get-started/)
 
 #### PostgreSQL headers
 
@@ -47,8 +64,28 @@ brew install postgresql
 
 For Windows:
 
-- No additional system dependencies required
-- Install Python from the official Python website
+- No installation required
+
+#### Quarto CLI and Graphviz
+
+- [Quarto CLI](https://quarto.org/docs/get-started/)
+
+
+For macOS:
+
+``` bash
+brew install graphviz
+```
+
+For Ubuntu/Debian:
+
+``` bash
+sudo apt update && sudo apt install -y graphviz
+```
+
+For Windows:
+
+- Download and install from [Graphviz.org](https://graphviz.org/download/#windows)
 
 #### Python dependencies