fix docker build and make container useful

[karl-denby]

This makes a few changes:

1. Container runs go 1.21, instead of 1.19 which is now a requirement of hatchet
2. Container build is fixed for the musl error it previously showed
3. build now copies hatchet to /bin in the container so you can just call hatchet instead of ./dist/hatchet each time
4. docker-compose file is included which will run the build if required, map port 3721 and mount ./logs into the container
5. README.md updated to include docker compose instructions and example