Constellation, Spacedust, Slingshot, UFOs: atproto crates and services for microcosm

feat: adds dockerfiles for constellation and slingshot #54

Merged microcosm.blue
targeting main from pds.dad/microcosm-rs:feature/Dockerfiles
Merged opened by and assigned to microcosm.blue
targeting main from pds.dad/microcosm-rs:feature/Dockerfiles

This PR adds dockerfiles for constellation and slingshot as well as a docker compose for an example on how to run them.

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