Filename mismatch: transform-use-async-functions.ts vs. transform-use-async-function.ts

[Tschoner]

The README references the file as transform-use-async-functions.ts, but the actual file in the repository is named transform-use-async-function.ts (no “s”).

Pull request [#6] addresses this issue by updating the filename in the README to match the actual file. It’s a minor fix, but worth mentioning to avoid any confusion. Thank you!