Changelog for https://github.com/cloudflare/workerd/pull/7053

### Proposed changes

here is a draft of a changelog for https://github.com/cloudflare/workerd/pull/7053

# Create AbortSignals outside request handlers in the Workers runtime

You can now create `AbortController` and `AbortSignal` objects during module initialization in Cloudflare Workers:

```js
const controller = new AbortController();
const alreadyCancelled = AbortSignal.abort("cancelled");

export default {
async fetch() {
return Response.json({
cancelled: alreadyCancelled.aborted,
});
},
};
```

This change brings Workers in line with browsers and Node.js. Libraries can now create controllers, requests, and writable streams when you import them without encountering an `IoContext` error.

You can also observe or abort a signal from a different request running in the same isolate. Workerd routes cancellation to the request that owns each pending operation.

Do not use isolate-local signals when your application requires durable cancellation. Cloudflare may route requests to another isolate or restart an isolate at any time. Use a Durable Object to coordinate those requests.

`AbortSignal.timeout()` still requires an active request because it schedules a timer.

## More consistent event handling

This change also aligns `EventTarget` behavior with the DOM standard:

- One listener throwing an exception no longer prevents later listeners from running.
- `abort()` no longer throws when an abort listener throws.
- Workerd reports listener exceptions through the global `error` event and console.
- Workerd removes listeners registered with `{ signal }` before it runs abort listeners.
- Events you construct report `isTrusted === false`.

Most applications require no changes.

### Subject Matter

https://github.com/cloudflare/workerd/pull/7053

### Content Location

new changelog. also research docs if there is anything we need to update, like warnings saying that you can't do what is now possible

### Additional information

_No response_

Review the proposed changelog text and the referenced workerd pull request 7053 first, then search the documentation for warnings about AbortController, AbortSignal, EventTarget, and request-handler-only usage. Done means adding the changelog and updating any outdated guidance identified by that search.

Written by the indexing model from the issue text.