Fix usage example (#35)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

Author: jonidelv

index.d.ts

@@ -136,7 +136,7 @@ const delayedPromise = () => setTimeout(200);
 await pTimeout(delayedPromise(), {
 	milliseconds: 50,
 	fallback: () => {
-		return pTimeout(delayedPromise(), 300);
+		return pTimeout(delayedPromise(), {milliseconds: 300});
 	}
 });
 ```

readme.md

@@ -86,7 +86,7 @@ const delayedPromise = () => setTimeout(200);
 await pTimeout(delayedPromise(), {
 	milliseconds: 50,
 	fallback: () => {
-		return pTimeout(delayedPromise(), 300);
+		return pTimeout(delayedPromise(), {milliseconds: 300});
 	},
 });
 ```