chore: Update syntax, improve more typing (#1439)

* chore: <React.Fragment> to <>

* flow types

app/types/index.js

@@ -1,6 +1,13 @@
 // @flow
+import { type Location } from "react-router-dom";
 import Document from "models/Document";
 
+export type LocationWithState = Location & {
+  state: {
+    [key: string]: string,
+  },
+};
+
 export type Toast = {
   id: string,
   createdAt: string,