Add flow types; related to #24

src/pages/docs/error-decoder.html.js

@@ -2,6 +2,7 @@
  * Copyright (c) 2013-present, Facebook, Inc.
  *
  * @emails react-core
+ * @flow
  */
 
 'use strict';
@@ -19,7 +20,12 @@ import {createLinkDocs} from 'utils/createLink';
 import findSectionForPath from 'utils/findSectionForPath';
 import {sectionListDocs} from 'utils/sectionList';
 
-const ErrorPage = ({data, location}) => (
+type Props = {
+  data: Object,
+  location: Location,
+};
+
+const ErrorPage = ({data, location}: Props) => (
   <Flex
     direction="column"
     grow="1"