chore: fix react-sdk REAMDE example, add missing EvaluationContext (#762)

## This PR
- fixes the example in react-sdk's REAMDE, add missing
`EvaluationContext`.

Signed-off-by: Henry Chen <[email protected]>

Author: chenhunghan

packages/react/README.md

@@ -33,7 +33,7 @@ Here's a basic example of how to use the current API with the in-memory provider
 ```tsx
 import logo from './logo.svg';
 import './App.css';
-import { OpenFeatureProvider, useFeatureFlag, OpenFeature } from '@openfeature/react-sdk';
+import { EvaluationContext, OpenFeatureProvider, useFeatureFlag, OpenFeature } from '@openfeature/react-sdk';
 import { FlagdWebProvider } from '@openfeature/flagd-web-provider';
 
 const flagConfig = {
@@ -168,4 +168,4 @@ function Fallback() {
   // component to render before READY.
   return <p>Waiting for provider to be ready...</p>;
 }
-```
+```