v2.1.1 — fix broken npm package

Fixed

• The published npm package was missing dist/browser/ — the WASM binary and its glue code —
  which made every import fail with ERR_MODULE_NOT_FOUND. wasm-pack writes a .gitignore
  containing * into its output directory and npm honours nested .gitignore files when packing,
  so the whole directory was silently dropped from the tarball. prepare.ts now removes that file
  along with the other wasm-pack leftovers. Affects 2.0.0 and 2.1.0, both unusable