0.3.0

CHANGES:

• Update to OCaml 5.
• Add support for many more symbols and currencies.
• Gracefully handle unknown currencies using new Enum_or_string abstraction.
• Websocket pipes now retain result types when processing json rather than raising
  exceptions inside the pipe (breaking change).
• Switch from websockets-async to simpler, better supported cohttp_async_websocket.
• Fix various parse errors due to new gemini fields.
• Format the codebase with ocamlformat.
• Added --no-csv option to disable csv generation from command line.
• Introduced Poly_ok utility module for unwrapping polymorphic variant result types.