Add responsive reducer

src/reducers/responsive.js

@@ -0,0 +1,16 @@
+const Responsive = (state = {
+  width: null,
+  height: null,
+}, action) => {
+  switch (action.type) {
+  case "resize event":
+    return Object.assign({}, state, {
+      width: action.data,
+      height: action.data
+    });
+  default:
+    return state;
+  }
+};
+
+export default Responsive;