Restore vanilla components

app/javascript/mastodon/reducers/cards.js

@@ -0,0 +1,14 @@
+import { STATUS_CARD_FETCH_SUCCESS } from '../actions/cards';
+
+import { Map as ImmutableMap, fromJS } from 'immutable';
+
+const initialState = ImmutableMap();
+
+export default function cards(state = initialState, action) {
+  switch(action.type) {
+  case STATUS_CARD_FETCH_SUCCESS:
+    return state.set(action.id, fromJS(action.card));
+  default:
+    return state;
+  }
+};