Add snack bar store

ui/src/stores/SnackBarStore.js

@@ -0,0 +1,25 @@
+import {EventEmitter} from 'events';
+import dispatcher from './dispatcher';
+
+class SnackBarStore extends EventEmitter {
+    messages = [];
+
+    next() {
+        return this.messages.shift();
+    }
+
+    hasNext() {
+        return this.messages.length !== 0;
+    }
+
+    handle(data) {
+        if (data.type === 'SNACK') {
+            this.messages.push(data.payload);
+            this.emit('change');
+        }
+    }
+}
+
+const store = new SnackBarStore();
+dispatcher.register(store.handle.bind(store));
+export default store;