upd(Dockerfile): Set program directory

Set program directory to have easier docker-compose recipe.

Signed-off-by: Denys Fedoryshchenko <denys.f@collabora.com>

Author: nuclearcat

Dockerfile

@@ -6,6 +6,8 @@ RUN cargo install --path .
 FROM debian:bookworm-slim
 RUN apt-get update && rm -rf /var/lib/apt/lists/*
 COPY --from=builder /usr/local/cargo/bin/kernelci-storage /usr/local/bin/kernelci-storage
+RUN mkdir /workdir
+WORKDIR /workdir
 CMD ["kernelci-storage"]