docs: ✏️ add useUnmountedPromise reference

Author: streamich

README.md

@@ -111,7 +111,7 @@
   - [`useMountedState`](./docs/useMountedState.md) — track if component is mounted.
   - [`usePromise`](./docs/usePromise.md) — resolves promise only while component is mounted.
   - [`useLogger`](./docs/useLogger.md) — logs in console as component goes through life-cycles.
-  - [`useMount`](./docs/useMount.md) — calls `mount` callbacks.
+  - [`useMount`](./docs/useMount.md) and [`useUnmountPromise`](./docs/useUnmountPromise.md) — tracks if component is mounted.
   - [`useUnmount`](./docs/useUnmount.md) — calls `unmount` callbacks.
   - [`useUpdateEffect`](./docs/useUpdateEffect.md) — run an `effect` only on updates.
   - [`useIsomorphicLayoutEffect`](./docs/useIsomorphicLayoutEffect.md) — `useLayoutEffect` that does not show warning when server-side rendering.

docs/useUnmountPromise.md

@@ -0,0 +1,30 @@
+# `useUnmountPromise`
+
+A life-cycle hook that provides a higher order promise that does not resolve if component un-mounts.
+
+
+## Usage 
+
+```ts
+import useUnmountPromise from 'react-use/lib/useUnmountPromise';
+
+const Demo = () => {
+  const mounted = useUnmountPromise();
+  useEffect(async () => {
+    await mounted(someFunction()); // Will not resolve if component un-mounts.
+  });
+};
+```
+
+
+## Reference
+
+```ts
+const mounted = useUnmountPromise();
+
+mounted(promise);
+mounted(promise, onError);
+```
+
+- `onError` — if promise rejects after the component is unmounted, `onError`
+  callback is called with the error.

src/index.ts

@@ -85,6 +85,7 @@ export { default as useTitle } from './useTitle';
 export { default as useToggle } from './useToggle';
 export { default as useTween } from './useTween';
 export { default as useUnmount } from './useUnmount';
+export { default as useUnmountPromise } from './useUnmountPromise';
 export { default as useUpdate } from './useUpdate';
 export { default as useUpdateEffect } from './useUpdateEffect';
 export { default as useUpsert } from './useUpsert';