message: chore(backend): add missing clean command to functions
diff: "test": "yarn run test:firestore && yarn run test:triggers",
  "lint": "eslint . --ext .ts && prettier --check \"./**/*.ts\"",
  "lint:fix": "eslint . --fix --ext .ts && prettier --write \"./**/*.ts\"",
  - "build": "rm -rf lib && tsc --build src/tsconfig.json",
  + "clean": "rm -rf lib ",
  + "build": "yarn run clean && tsc --build src/tsconfig.json",
  "serve": "yarn run build && firebase emulators:start",
  "shell": "yarn run build && firebase functions:shell",
  "start": "yarn run shell",
  