Update isPending and startTransition

Per [20976](facebook/react#20976), appears that isPending is now the first parameter.

Author: clive-h-townsend

content/docs/concurrent-mode-patterns.md

@@ -79,16 +79,16 @@ Finally, we'll use it inside the `App` component:
 ```js{3-5}
 function App() {
   const [resource, setResource] = useState(initialResource);
-  const [startTransition, isPending] = useTransition({
+  const [isPending, startTransition] = useTransition({
     timeoutMs: 3000
   });
   // ...
 ```
 
 **By itself, this code doesn't do anything yet.** We will need to use this Hook's return values to set up our state transition. There are two values returned from `useTransition`:
 
-* `startTransition` is a function. We'll use it to tell React *which* state update we want to defer.
 * `isPending` is a boolean. It's React telling us whether that transition is ongoing at the moment.
+* `startTransition` is a function. We'll use it to tell React *which* state update we want to defer.
 
 We will use them right below.
 
@@ -130,10 +130,10 @@ If we make our API responses take 5 seconds, [we can confirm](https://codesandbo
 
 There's still something that feels broken about [our last example](https://codesandbox.io/s/musing-driscoll-6nkie). Sure, it's nice not to see a "bad" loading state. **But having no indication of progress at all feels even worse!** When we click "Next", nothing happens and it feels like the app is broken.
 
-Our `useTransition()` call returns two values: `startTransition` and `isPending`.
+Our `useTransition()` call returns two values: `isPending` and `startTransition`.
 
 ```js
-  const [startTransition, isPending] = useTransition({ timeoutMs: 3000 });
+  const [isPending, startTransition] = useTransition({ timeoutMs: 3000 });
 ```
 
 We've already used `startTransition` to wrap the state update. Now we're going to use `isPending` too. React gives this boolean to us so we can tell whether **we're currently waiting for this transition to finish**. We'll use it to indicate that something is happening:
@@ -169,7 +169,7 @@ Let's take another look at all the changes we've made since the [original exampl
 ```js{3-5,9,11,14,19}
 function App() {
   const [resource, setResource] = useState(initialResource);
-  const [startTransition, isPending] = useTransition({
+  const [isPending, startTransition] = useTransition({
     timeoutMs: 3000
   });
   return (
@@ -261,7 +261,7 @@ However, the experience feels really jarring. We were browsing a page, but it go
 
 ```js{2-5,9-11,21}
 function ProfilePage() {
-  const [startTransition, isPending] = useTransition({
+  const [isPending, startTransition] = useTransition({
     // Wait 10 seconds before fallback
     timeoutMs: 10000
   });
@@ -302,7 +302,7 @@ This can lead to a lot of repetitive code across components. This is why **we ge
 
 ```js{7-9,20,24}
 function Button({ children, onClick }) {
-  const [startTransition, isPending] = useTransition({
+  const [isPending, startTransition] = useTransition({
     timeoutMs: 10000
   });
 
@@ -550,7 +550,7 @@ Our `Button` component will immediately show the Pending state indicator on clic
 
 ```js{2,13}
 function Button({ children, onClick }) {
-  const [startTransition, isPending] = useTransition({
+  const [isPending, startTransition] = useTransition({
     timeoutMs: 10000
   });
 
@@ -681,7 +681,7 @@ As we mentioned earlier, if some state update causes a component to suspend, tha
 function App() {
   const [query, setQuery] = useState(initialQuery);
   const [resource, setResource] = useState(initialResource);
-  const [startTransition, isPending] = useTransition({
+  const [isPending, startTransition] = useTransition({
     timeoutMs: 5000
   });