add Dockerfile for demo example

Author: 0xmountaintop

Dockerfile

@@ -0,0 +1,12 @@
+FROM rustlang/rust:nightly as build
+WORKDIR multi-party-ecdsa
+COPY ./ ./
+RUN cargo build --release --examples
+
+FROM ubuntu:18.04
+WORKDIR multi-party-ecdsa
+COPY --from=build /multi-party-ecdsa/target/release/examples/sm_manager .
+COPY --from=build /multi-party-ecdsa/target/release/examples/gg18_keygen_client .
+COPY --from=build /multi-party-ecdsa/target/release/examples/gg18_sign_client .
+
+EXPOSE 8001