Fix syntax highlighting for JSX.

Author: ghengeveld

Diff for: README.md

@@ -144,7 +144,7 @@ factory function. Each has its unique benefits and downsides.
 The `useAsync` hook (available [from React v16.8.0](https://reactjs.org/hooks)) offers direct access to React Async's
 core functionality from within your own function components:
 
-```js
+```jsx
 import { useAsync } from "react-async"
 
 const loadCustomer = async ({ customerId }, { signal }) => {
@@ -170,7 +170,7 @@ const MyComponent = () => {
 
 Or using the shorthand version:
 
-```js
+```jsx
 const MyComponent = () => {
   const { data, error, isLoading } = useAsync(loadCustomer, options)
   // ...
@@ -181,7 +181,7 @@ const MyComponent = () => {
 
 Because fetch is so commonly used with `useAsync`, there's a dedicated `useFetch` hook for it:
 
-```js
+```jsx
 import { useFetch } from "react-async"
 
 const MyComponent = () => {
@@ -204,7 +204,7 @@ is set to `"application/json"`.
 The classic interface to React Async. Simply use `<Async>` directly in your JSX component tree, leveraging the render
 props pattern:
 
-```js
+```jsx
 import Async from "react-async"
 
 // Your promiseFn receives all props from Async and an AbortController instance
@@ -237,7 +237,7 @@ Several [helper components](#helper-components) are available for better legibil
 children of `<Async>`, because they use Context, offering full flexibility. You can even use render props and helper
 components together.
 
-```js
+```jsx
 import Async from "react-async"
 
 const loadCustomer = ({ customerId }, { signal }) =>
@@ -266,7 +266,7 @@ const MyComponent = () => (
 You can also create your own component instances, allowing you to preconfigure them with options such as default
 `onResolve` and `onReject` callbacks.
 
-```js
+```jsx
 import { createInstance } from "react-async"
 
 const loadCustomer = ({ customerId }, { signal }) =>
@@ -539,15 +539,15 @@ Renders only while the deferred promise is still waiting to be run, or you have
 
 #### Examples
 
-```js
+```jsx
 <Async deferFn={deferFn}>
   <Async.Initial>
     <p>This text is only rendered while `run` has not yet been invoked on `deferFn`.</p>
   </Async.Initial>
 </Async>
 ```
 
-```js
+```jsx
 <Async.Initial persist>
   {({ error, isPending, run }) => (
     <div>
@@ -574,13 +574,13 @@ Alias: `<Async.Loading>`
 
 #### Examples
 
-```js
+```jsx
 <Async.Pending initial>
   <p>This text is only rendered while performing the initial load.</p>
 </Async.Pending>
 ```
 
-```js
+```jsx
 <Async.Pending>{({ startedAt }) => `Loading since ${startedAt.toISOString()}`}</Async.Pending>
 ```
 
@@ -597,11 +597,11 @@ Alias: `<Async.Resolved>`
 
 #### Examples
 
-```js
+```jsx
 <Async.Fulfilled persist>{data => <pre>{JSON.stringify(data)}</pre>}</Async.Fulfilled>
 ```
 
-```js
+```jsx
 <Async.Fulfilled>{(data, { finishedAt }) => `Last updated ${finishedAt.toISOString()}`}</Async.Fulfilled>
 ```
 
@@ -616,11 +616,11 @@ This component renders only when the promise is rejected.
 
 #### Examples
 
-```js
+```jsx
 <Async.Rejected persist>Oops.</Async.Rejected>
 ```
 
-```js
+```jsx
 <Async.Rejected>{error => `Unexpected error: ${error.message}`}</Async.Rejected>
 ```
 
@@ -642,7 +642,7 @@ check out the [`examples` directory](https://github.com/ghengeveld/react-async/t
 
 This does some basic data fetching, including a loading indicator, error state and retry.
 
-```js
+```jsx
 class App extends Component {
   getSession = ({ sessionId }) => fetch(...)
 
@@ -677,7 +677,7 @@ class App extends Component {
 
 This uses `deferFn` to trigger an update (e.g. POST / PUT request) after a form submit.
 
-```js
+```jsx
 const subscribeToNewsletter = (args, props, controller) => fetch(...)
 
 <Async deferFn={subscribeToNewsletter}>
@@ -697,7 +697,7 @@ const subscribeToNewsletter = (args, props, controller) => fetch(...)
 
 This uses both `promiseFn` and `deferFn` along with `setData` to implement optimistic updates.
 
-```js
+```jsx
 const updateAttendance = ([attend]) => fetch(...).then(() => attend, () => !attend)
 
 <Async promiseFn={getAttendance} deferFn={updateAttendance}>
@@ -718,7 +718,7 @@ const updateAttendance = ([attend]) => fetch(...).then(() => attend, () => !atte
 
 This uses `initialValue` to enable server-side rendering with Next.js.
 
-```js
+```jsx
 static async getInitialProps() {
   // Resolve the promise server-side
   const customers = await loadCustomers()