Add Dockerfile and compose config for testing

contrib/images/Dockerfile

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+ARG PYTHON_IMG_TAG
+FROM python:${PYTHON_IMG_TAG}-slim-bookworm as base
+
+
+FROM base as build
+RUN set -ex \
+    && apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install \
+    -y --no-install-recommends \
+        "build-essential" \
+    && rm -rf /var/lib/apt/lists/*
+WORKDIR /code
+COPY ../../ ./
+# Install with dev dependencies for tests
+RUN pip install .[dev] \
+    --user --no-warn-script-location --no-cache-dir
+
+
+FROM base as runtime
+ENV PATH="/root/.local/bin:$PATH"
+RUN set -ex \
+    && apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install \
+    -y --no-install-recommends \
+        "openjdk-17-jdk" \
+    && rm -rf /var/lib/apt/lists/*
+# Copy Python deps from build to runtime
+COPY --from=build \
+    /root/.local \
+    /root/.local
+WORKDIR /code
+ENTRYPOINT ["xlsform"]

contrib/images/docker-compose.yml

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+
+version: "3"
+
+name: pyxform
+
+services:
+  pyxform:
+    image: "ghcr.io/xlsform/pyxform:ci"
+    build:
+      context: ../../
+      dockerfile: contrib/images/Dockerfile
+      target: runtime
+      args:
+        PYTHON_IMG_TAG: "${PYTHON_IMG_TAG:-3.10}"
+    volumes:
+      - ../../tests:/code/tests
+      - ../../pyxform:/root/.local/lib/python3.10/site-packages/pyxform
+    entrypoint: ["python", "-m", "unittest", "--verbose"]
+    restart: "unless-stopped"