Misc. ingredients (e.g. Irish Moss by volume)

I couldn't find a place to note my Irish Moss addition. Granted, that's more of a "process" than "recipe" thing, but it'd be nice to have.

No file, test, or entry point is named. Start by tracing how recipe additions and process notes are currently recorded, then determine how an Irish Moss addition by volume should be represented. Done means the chosen behavior is implemented and covered by tests.

Written by the indexing model from the issue text.