message: Add `*.tsbuildinfo` to `.gitignore`
  These are produced by TypeScript 3.4 to support incremental compilation, see
diff: node_modules
  lib
  +# TypeScript incremental compilation cache
  +*.tsbuildinfo
  +
  # Only the top-level of the monorepo should govern package locks,
  # not the individual package directories. (Keep in mind that currently
  # `npm install` should not be run within the `packages/*` directories.)
  