Allow Redux DevTools browser extension to be used. (#13)

README.md

@@ -80,6 +80,10 @@ There are end-to-end tests that run on Nightwatch. This selenium-based test runn
 
 To set up credentials and run the tests, check out the [README](/tests/README.md) in `/tests/.
 
+## Debugging
+
+The [Redux DevTools browser extension](https://github.com/reduxjs/redux-devtools/tree/main/extension) may be used to easily inspect app states and state transitions.
+
 ## License
 
 ```

src/store.ts

@@ -1,4 +1,5 @@
 import {
+  compose,
   createStore,
   combineReducers,
   applyMiddleware,
@@ -14,8 +15,15 @@ const reducers: Reducer = combineReducers({
   catalog: catalogReducers,
 });
 
+const composeEnhancers =
+  window["__REDUX_DEVTOOLS_EXTENSION_COMPOSE__"] || compose;
+
 /** Build a redux store with reducers specific to the admin interface
     as well as reducers from opds-web-client. */
 export default function buildStore(initialState?: State): Store<State> {
-  return createStore(reducers, initialState, applyMiddleware(thunk));
+  return createStore(
+    reducers,
+    initialState,
+    composeEnhancers(applyMiddleware(thunk))
+  );
 }