Update jsdocs for hooks (#1295)

* Make second argument to useSelector optional

* Update useDispatch jsdoc return

src/hooks/useDispatch.js

@@ -5,7 +5,7 @@ import { useStore } from './useStore'
  * might want to use this hook it is recommended to use `useActions` instead to bind
  * action creators to the `dispatch` function.
  *
- * @returns {any} redux store's `dispatch` function
+ * @returns {any|function} redux store's `dispatch` function
  *
  * @example
  *

src/hooks/useSelector.js

@@ -25,7 +25,7 @@ const refEquality = (a, b) => a === b
  * whether the component needs to be re-rendered.
  *
  * @param {Function} selector the selector function
- * @param {Function} equalityFn the function that will be used to determine equality
+ * @param {Function=} equalityFn the function that will be used to determine equality
  *
  * @returns {any} the selected state
  *