expose websocket electrs API using websocat

[louisinger]

• entrypoint.sh is running electrs & websocat in background.
• @tiero should we fetch the websocat binary instead of building it?

[tiero]

rust is very slow to being build, you can fetch binaries using COPY in dockerfile

ie. COPY --from=ghcr.io/image:latest /usr/local/bin/* /usr/local/bin/