Grabbed dndbeyond's source code

```
~/go/bin/sourcemapper -output ddb -jsurl https://media.dndbeyond.com/character-app/static/js/main.90aa78c5.js
```

ddb_main/tools/js/Shared/reducers/appInfo.ts

@@ -0,0 +1,29 @@
+import { appInfoActionTypes } from "../actions/appInfo";
+import { AppInfoAction } from "../actions/appInfo/typings";
+import { AppInfoState } from "../stores/typings";
+
+const initialState: AppInfoState = {
+  error: null,
+};
+function appInfo(
+  state: AppInfoState = initialState,
+  action: AppInfoAction
+): AppInfoState {
+  switch (action.type) {
+    case appInfoActionTypes.ERROR_SET:
+      return {
+        ...state,
+        error: {
+          type: action.payload.appErrorType,
+          errorId: action.payload.errorId,
+        },
+      };
+
+    default:
+    // not implemented
+  }
+
+  return state;
+}
+
+export default appInfo;