docs: add devcontainer quickstart for GUAC

guac/dev-setup.md

@@ -9,6 +9,56 @@ nav_order: 6
 
 # Development environment setup
 
+## Try GUAC with a dev container
+
+A [development container](https://containers.dev/) is a quick way to try GUAC
+without installing its Go build tools locally. The GUAC repository includes a
+[`.devcontainer/devcontainer.json`](https://github.com/guacsec/guac/blob/main/.devcontainer/devcontainer.json)
+configuration that downloads a published GUAC image and starts the services
+using Docker Compose.
+
+Choose either of these environments:
+
+- **GitHub Codespaces:** Open the
+  [GUAC repository](https://github.com/guacsec/guac), select **Code**,
+  **Codespaces**, then **Create codespace on main**.
+- **VS Code locally:** Install [Docker](https://docs.docker.com/get-docker/) and
+  the
+  [Dev Containers extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers).
+  Clone `https://github.com/guacsec/guac.git`, open the repository in VS Code,
+  and select **Dev Containers: Reopen in Container** from the Command Palette.
+
+The first startup pulls the GUAC release image. On each container start, its
+`postStartCommand` launches the in-memory backend using `docker-compose.yml` and
+`container_files/mem.yaml`. Wait for the terminal message `GUAC is ready.`
+
+Open the forwarded **8080** port to access the GraphQL playground. The REST API
+is exposed on port **8081**, and you can check its health at
+`http://localhost:8081/healthz` from inside the dev container (or through the
+forwarded port).
+
+From a terminal in the GUAC repository, you can manage the services:
+
+```bash
+# Show service status
+docker compose -f docker-compose.yml -f container_files/mem.yaml ps
+
+# Follow logs when debugging startup
+docker compose -f docker-compose.yml -f container_files/mem.yaml logs -f
+
+# Stop the services when you are done
+docker compose -f docker-compose.yml -f container_files/mem.yaml down
+```
+
+The default backend is in memory, so it is intended for experimentation, not
+durable storage. For a PostgreSQL-backed setup, replace
+`container_files/mem.yaml` with `container_files/ent.yaml` in the devcontainer's
+`postStartCommand` before reopening the container. See the [GraphQL
+guide]({{ site.baseurl }}{% link guac/guac-graphql.md %}) for query and
+ingestion examples.
+
+## Install tools for manual development
+
 ## Ensure you have the following tools installed in your environment
 
 - [Docker](https://docs.docker.com/get-docker/)