message: Move event typing to dependencies
  EventEmitter is used in an exported type, so it is a required dependencies instead of dev dependencies.
diff: },
  "dependencies": {
  "@fluidframework/common-definitions": "^0.19.1-0",
  + "@types/events": "^3.0.0",
  "assert": "^2.0.0",
  "base64-js": "^1.3.1",
  "events": "^3.1.0",
  "@microsoft/api-extractor": "^7.7.2",
  "@types/assert": "^1.5.1",
  "@types/benchmark": "^1.0.31",
  - "@types/events": "^3.0.0",
  "@types/jest": "22.2.3",
  "@types/jest-environment-puppeteer": "2.2.0",
  "@types/mocha": "^5.2.5",
  