Upload media files and store in redux store

Summary:
This diff adds the media files into the redux store. In the redux store they are stored as the following {fbid: description}, where fbid and description are integer and string respectively.

Ignore the rows getting highlighted automatically, there seems to be a bug in the ManagedTable. Talked to Michel and we agreed to replace it.

Reviewed By: mweststrate

Differential Revision: D18708815

fbshipit-source-id: 0aaf1b672c230312203691538091a717d69fb5ad

src/reducers/supportForm.tsx

@@ -8,13 +8,14 @@
  */
 
 import {Actions} from './';
+export type MediaType = Array<{uri: string; description: string}>;
 export type SupportFormV2State = {
   title: string;
   description: string;
   commitHash: string;
   appName: string;
-  screenshots?: {image: string; description: string}[];
-  videos?: {url: string; description: string}[];
+  screenshots?: MediaType;
+  videos?: MediaType;
 };
 
 export type State = {