message: Add node engine compatibility spec
diff: "version": "0.50.1",
  "description": "iModelJs backend components",
  "license": "UNLICENSED",
  + "engines": {
  + "node": ">=8.9.0 <9.0"
  + },
  "scripts": {
  "build": "tsc && npm run copy:assets",
  "clean": "rimraf lib",
  