message: build: use linkinator for docs test
diff: "posttest": "npm run check",
  "proto": "npm run proto:logging",
  "proto:logging": "mkdir -p proto && pbjs -t static-module -w commonjs -p node_modules/google-proto-files google/logging/v2/logging.proto | pbts -o proto/logging.d.ts -",
  - "docs-test": "blcl docs -r --exclude www.googleapis.com",
  + "docs-test": "linkinator docs -r --skip www.googleapis.com",
  "predocs-test": "npm run docs"
  },
  "dependencies": {
  "proxyquire": "^2.1.0",
  "typescript": "~3.3.0",
  "uuid": "^3.3.2",
  - "broken-link-checker-local": "^0.2.0"
  + "linkinator": "^1.1.2"
  }
  }
  