Add instructions on connecting firmware board device

[LongLiveCHIEF]

The only place where there are any instructions on connecting USB devices to the container is in the docker-compose.yml file, and those aren't really instructions, it's just a commented out device mapping for possible device configurations.

There is a broken link for initial setup in the README that I believe used to have a small section about mapping your printers motherboard to the docker-container.

• repair remove the initial setup link
• add brief instructions on mapping devices to docker container
• annotate docker-compose.yml with comments for the devices config block giving a hint for users to uncomment the correct device for their purposes