This schema allows clients to send Black Market info derived from "MarketSell" entries in the "Commander's Log" Journal to EDDN. The schema is based on pre-release info so this PR will likely need to be updated during the E:D 2.2 beta run.
The schema is loosely based on the commodity/3 schema, but note that values of the "name" property are different between commodity/3 and blackmarket/1 messages - e.g. "Mineral Oil" v "mineraloil".
Here is an example message in this schema.