add router in index.js

src/server/routes/apiv3/index.js

@@ -41,6 +41,7 @@ module.exports = (crowi) => {
   router.use('/pages', require('./pages')(crowi));
 
   router.use('/bookmarks', require('./bookmarks')(crowi));
+  router.use('/attachment', require('./attachment')(crowi));
 
   return router;
 };