Update README with React usage example

Author: ploomiz

README.md

@@ -8,3 +8,52 @@ This SDK is for client-side JS applications that run in a web browser. For serve
 ## Getting Started
 
 Refer to our [SDK documentation](https://docs.geteppo.com/feature-flagging/randomization-sdk) for how to install and use the SDK.
+
+## Usage with React
+
+For usage in React applications, we recommend creating a [Context](https://reactjs.org/docs/context.html) provider to intialize the SDK and store the initialization status.
+
+```tsx
+import { useEffect, useState, createContext } from 'react';
+import * as EppoSdk from '@eppo/js-client-sdk';
+
+const EppoContext = createContext({ isInitialized: false });
+
+function EppoProvider({ children }): JSX.Element {
+  const [isInitialized, setIsInitialized] = useState(false);
+
+  useEffect(() => {
+    EppoSdk.init({ apiKey: '<API-KEY>' })
+      .then(() => setIsInitialized(true));
+  }, []);
+
+  return (
+     <EppoContext.Provider value={{ isInitialized }}>
+        {children}
+     </EppoContext.Provider>
+  );
+}
+```
+
+Use the context provider at the root of your component tree to wrap the rest of your application:
+
+```tsx
+<EppoProvider>
+   <MyApp />
+</EppoProvider>
+```
+
+React components in your application should consume the context to check that the SDK has been initialized before assigning a variation. (Alternatively, you could have the `EppoProvider` wait to render its children until the SDK is initialized.)
+
+```tsx
+import { useContext } from 'react';
+import * as EppoSdk from '@eppo/js-client-sdk';
+
+const { isInitialized } = useContext(EppoContext);
+if (isInitialized) {
+  const assignedVariation = EppoSdk.getInstance().getAssignment(subjectKey, experimentKey);
+  ...
+}
+```
+
+