Update transition docs for React 19 (#6837)

* Add async transitions to React 19 docs

* Updates from feedback

* tweaks

* grammar

* Add startTranstion API

* Apply suggestions from code review

Co-authored-by: Noah Lemen <[email protected]>

* Updated

* capitalization

* grammar

---------

Co-authored-by: Noah Lemen <[email protected]>

Author: rickhanlonii

src/content/reference/react/startTransition.md

@@ -4,10 +4,10 @@ title: startTransition
 
 <Intro>
 
-`startTransition` lets you update the state without blocking the UI.
+`startTransition` lets you render a part of the UI in the background.
 
 ```js
-startTransition(scope)
+startTransition(action)
 ```
 
 </Intro>
@@ -18,7 +18,7 @@ startTransition(scope)
 
 ## Reference {/*reference*/}
 
-### `startTransition(scope)` {/*starttransitionscope*/}
+### `startTransition(action)` {/*starttransition*/}
 
 The `startTransition` function lets you mark a state update as a Transition.
 
@@ -41,7 +41,7 @@ function TabContainer() {
 
 #### Parameters {/*parameters*/}
 
-* `scope`: A function that updates some state by calling one or more [`set` functions.](/reference/react/useState#setstate) React immediately calls `scope` with no arguments and marks all state updates scheduled synchronously during the `scope` function call as Transitions. They will be [non-blocking](/reference/react/useTransition#marking-a-state-update-as-a-non-blocking-transition) and [will not display unwanted loading indicators.](/reference/react/useTransition#preventing-unwanted-loading-indicators)
+* `action`: A function that updates some state by calling one or more [`set` functions](/reference/react/useState#setstate). React calls `action` immediately with no parameters and marks all state updates scheduled synchronously during the `action` function call as Transitions. Any async calls awaited in the `action` will be included in the transition, but currently require wrapping any `set` functions after the `await` in an additional `startTransition` (see [Troubleshooting](#react-doesnt-treat-my-state-update-after-await-as-a-transition)). State updates marked as Transitions will be [non-blocking](#marking-a-state-update-as-a-non-blocking-transition) and [will not display unwanted loading indicators.](#preventing-unwanted-loading-indicators).
 
 #### Returns {/*returns*/}
 
@@ -53,13 +53,15 @@ function TabContainer() {
 
 * You can wrap an update into a Transition only if you have access to the `set` function of that state. If you want to start a Transition in response to some prop or a custom Hook return value, try [`useDeferredValue`](/reference/react/useDeferredValue) instead.
 
-* The function you pass to `startTransition` must be synchronous. React immediately executes this function, marking all state updates that happen while it executes as Transitions. If you try to perform more state updates later (for example, in a timeout), they won't be marked as Transitions.
+* The function you pass to the of `startTransition` is called immediately, marking all state updates that happen while it executes as Transitions. If you try to perform state updates in a `setTimeout`, for example, they won't be marked as Transitions.
+
+* You must wrap any state updates after any async requests in another `startTransition` to mark them as Transitions. This is a known limitation that we will fix in the future (see [Troubleshooting](#react-doesnt-treat-my-state-update-after-await-as-a-transition)).
 
 * A state update marked as a Transition will be interrupted by other state updates. For example, if you update a chart component inside a Transition, but then start typing into an input while the chart is in the middle of a re-render, React will restart the rendering work on the chart component after handling the input state update.
 
 * Transition updates can't be used to control text inputs.
 
-* If there are multiple ongoing Transitions, React currently batches them together. This is a limitation that will likely be removed in a future release.
+* If there are multiple ongoing Transitions, React currently batches them together. This is a limitation that may be removed in a future release.
 
 ---