Document the project and parameterize defaults

README.md

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+# docker-comfyui
+
+Build and run ComfyUI in a container. This build targets NVIDIA by basing it
+on the CUDA PyTorch runtime image. The only extra dependencies needed are
+`git`, to clone the official ComfyUI repository, and `build-essential` for
+`gcc`, which Triton requires. The image pulls a specific, pinned ComfyUI
+version via the `COMFYUI_VERSION` build arg. The build merely shallow-clones
+the repo and installs its requirements with `pip`. Kept intentionally simple.
+
+### Quick start
+
+1. Build
+
+    ```
+    docker compose build
+    ```
+
+2. Run
+
+    ```
+    docker compose up -d
+    ```