Added useLocale hook.

hooks/useLocale.js

@@ -0,0 +1,13 @@
+import { useDispatch, useSelector } from 'react-redux';
+import { updateApp } from 'redux/actions/app';
+
+export default function useLocale() {
+  const locale = useSelector(state => state.app.locale);
+  const dispatch = useDispatch();
+
+  function setLocale(value) {
+    dispatch(updateApp({ locale: value }));
+  }
+
+  return [locale, setLocale];
+}