message: refactor(step-generation): point types and main to correct files
diff: "private": true,
  "version": "4.3.1",
  "description": "Step generation",
  - "main": "lib/main.js",
  - "types": "lib/main.d.ts",
  + "main": "lib/index.js",
  + "types": "lib/index.d.ts",
  "flow:main": "flow-types/index.js.flow",
  "bugs": {
  "url": "https://github.com/Opentrons/opentrons/issues"
  