2.5.1

Various fixes & improvements

• fix(produce): Fix closing next step (#183) by @lynnagara
• fix(reduce): Ensure next step is properly closed (#182) by @lynnagara
• ref: Don't alias ProcessingStrategy as ProcessingStep (#181) by @lynnagara
• ref: upgrade isort to work around poetry breakage (#179) by @asottile-sentry
• fix: Documentation typos (#178) by @markstory
• build: Split avro, json, msgpack into separate modules (#176) by @lynnagara