Add counter example; fix configuration

examples/accident-counter/src/reducer.ts

@@ -0,0 +1,29 @@
+type CounterState = {
+  count: number;
+};
+
+type CounterAction =
+  | { type: 'increment' }
+  | { type: 'decrement' }
+  | { type: 'reset' };
+
+export function reducer(
+  state: CounterState = { count: 0 },
+  action: CounterAction,
+): CounterState {
+  if (!action) return state;
+
+  switch (action.type) {
+    case 'increment':
+      return { count: state.count + 1 };
+    case 'decrement':
+      if (state.count > 0) {
+        return { count: state.count - 1 };
+      }
+      return { count: 0 };
+    case 'reset':
+      return { count: 0 };
+    default:
+      return state;
+  }
+}