refactor to share downloading code across all formats

src/components/views/rooms/RoomHeader.js

@@ -84,11 +84,11 @@ export default class RoomHeader extends React.Component {
     _exportConversationalHistory = async () => {
         await exportConversationalHistory(
             this.props.room,
-            exportFormats.JSON,
+            exportFormats.PLAIN_TEXT,
             exportTypes.START_DATE,
             {
                 startDate: parseInt(new Date("2021.05.20").getTime().toFixed(0)),
-                attachmentsIncluded: false,
+                attachmentsIncluded: true,
                 maxSize: 7 * 1024 * 1024, // 7 MB
             },
         );