Align TypeScript definitions and argument names with fetch API

This version improves the TypeScript definition of the wrapping function.

Previously it would simply expect a function with the same signature as the fetch function. Now it expects to receive the actual fetch function.

In addition, the argument names used by fetch-retry now corresponds to the argument names used by the official fetch API.

Many thanks to @vishalvijay for highlighting the issue and providing the PR to fix it.