Update Dockerfile example, need to COPY README.md and pyproject.toml

Going back to the Dockerfile example, I saw that `uv pip install ...` required a pyproject.toml and README.md file (generated by `rye init`). You therefore need to copy them into the Dockerfile (which is not specified).

docs/guide/docker.md

@@ -22,7 +22,7 @@ This guide requires some familiarity with Docker and Dockerfiles.
     RUN pip install uv
 
     WORKDIR /app
-    COPY requirements.lock ./
+    COPY README.md pyproject.toml requirements.lock ./
     RUN uv pip install --no-cache --system -r requirements.lock
 
     COPY src .