adding docs subtree

docs/step2-06/exercise/src/reducers/reducer.spec.ts

@@ -0,0 +1,20 @@
+import { createStore } from 'redux';
+import { reducer } from '.';
+import { actions } from '../actions';
+
+describe('reducers', () => {
+  it('should add items', () => {
+    // 1. use Redux's createStore() to create a store with reducer as argument
+    // along with the initial state
+    //
+    // 2. call store.dispatch() with some action messages to indicate the kind of
+    // action to perform (in this case, addTodo)
+    //
+    // 3. assert with expect() on the resultant store.getState().todos
+  });
+
+  // Tests left for you to do:
+  // - remove
+  // - clear
+  // - complete
+});