Document how to use a persistent datomic db

Using an in-memory database and reloading data on every reset is quite annoying.

I've already figured out one way using docker to spin a persistent datomic instance on the FS, I'm exploring a little more on it and if it works I'll update the docs.

No file, test, or documentation entry point is named. Start by locating the existing database setup and documentation, then review the proposed Docker-based persistent Datomic setup. Done means documenting a confirmed persistent-database workflow and updating the relevant usage instructions.

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