message: Re-add postpack script
  ## Description
  Something seems to have gone wrong with a merge in a recent PR  I think) that removed a new npm script added to packages/dds/tree when merging `main` to `next`. Restoring it so the Performance benchmarks pipeline doesn't fail when it runs for the `next` branch.
diff: "format": "npm run prettier:fix",
  "lint": "npm run prettier && npm run eslint",
  "lint:fix": "npm run prettier:fix && npm run eslint:fix",
  + "postpack": "tar -cf ./tree.test-files.tar ./src/test ./dist/test",
  "prettier": "prettier --check . --ignore-path ../../../.prettierignore",
  "prettier:fix": "prettier --write . --ignore-path ../../../.prettierignore",
  "test": "npm run test:mocha",
  