Add more documentation (#3)

Author: zanieb

README.md

@@ -4,7 +4,7 @@ An example project for using uv in Dockerfiles.
 
 See the [uv Docker integration guide](https://docs.astral.sh/uv/guides/integration/docker/) for more details.
 
-## Running the image
+## Trying it out
 
 A [`run.sh`](./run.sh) utility is provided for quickly building the image and starting a container.
 
@@ -28,3 +28,35 @@ To enter a `bash` shell in the image:
 ```
 ./run.sh /bin/bash
 ```
+
+## Project overview
+
+### Dockerfile
+
+The [`Dockerfile`](./Dockerfile) defines the image and includes:
+
+- Installation of uv
+- Installing the project dependencies and the project separately for optimal image build caching
+- Placing environment executables on the `PATH`
+
+### Docker ignore file
+
+The [`.dockerignore`](./.dockerignore) file includes an entry for the `.venv` directory to ensure the
+`.venv` is not included in image builds. Note that the `.dockerignore` file is not applied to volume
+mounts during container runs.
+
+### Run script
+
+The [run script](./run.sh) includes an example of invoking `docker run` for local development,
+mounting the source code for the project into the container so that edits are reflected immediately.
+
+### Application code
+
+The Python application code for the project is at
+[`src/uv_docker_example/__init__.py`](./src/uv_docker_example/__init__.py) — it just prints hello
+world.
+
+### Project definition
+
+The project at [`pyproject.toml`](./pyproject.toml) includes includes Ruff as an example development
+dependency and defines a `hello` entrypoint for the application.