Correct AsyncProgressWorker link in README (#716)

* Correct AsyncProgressWorker link in README

Author: japj

README.md

@@ -115,7 +115,7 @@ The following is the documentation for node-addon-api.
 -[Async Operations](doc/async_operations.md)
 -[AsyncWorker](doc/async_worker.md)
 -[AsyncContext](doc/async_context.md)
--[AsyncProgressWorker](doc/async_progress_worker.md)
+-[AsyncWorker Variants](doc/async_worker_variants.md)
 -[Thread-safe Functions](doc/threadsafe_function.md)
 -[Promises](doc/promises.md)
 -[Version management](doc/version_management.md)