Fix PATH and ENTRYPOINT/CMD

mdbook/Dockerfile

@@ -3,5 +3,9 @@ LABEL maintainer="Ryan <ryan@helloryan.se>"
 
 RUN apk add rust cargo minio-client
 RUN cargo install mdbook
-ENV PATH="/root/.cargo/bin"
-ENTRYPOINT ["/root/.cargo/bin/mdbook"]
+ENV PATH="/root/.cargo/bin:$PATH"
+
+RUN printf "#!/bin/sh\n\$@\n" > /entrypoint.sh && chmod +x /entrypoint.sh
+
+ENTRYPOINT ["/entrypoint.sh"]
+CMD ["/root/.cargo/bin/mdbook"]