docs(service-worker): note that registerWhenStable requires a timeout

`registerWhenStable` without a `:<timeout>` does not wait for the
application to stabilize. It registers the ServiceWorker immediately, so
the JSDoc promising the opposite sends readers to the one form of the
strategy that does not do what they want.

Suggested in angular#71018.

Author: erkamyaman

adev/src/content/ecosystem/service-workers/getting-started.md

@@ -256,6 +256,7 @@ export const appConfig: ApplicationConfig = {
 Available registration strategies:
 
 - **`'registerWhenStable:timeout'`** (default: `'registerWhenStable:30000'`) - Register as soon as the application stabilizes (no pending micro-/macro-tasks) but no later than the specified timeout in milliseconds
+  The timeout is required. Without it, `'registerWhenStable'` registers the service worker immediately.
 - **`'registerImmediately'`** - Register the service worker immediately
 - **`'registerWithDelay:timeout'`** - Register with a delay of the specified timeout in milliseconds
 

packages/service-worker/src/provider.ts

@@ -198,8 +198,8 @@ export abstract class SwRegistrationOptions {
    *     micro-/macro-tasks) but no later than `<timeout>` milliseconds. If the app hasn't
    *     stabilized after `<timeout>` milliseconds (for example, due to a recurrent asynchronous
    *     task), the ServiceWorker will be registered anyway.
-   *     If `<timeout>` is omitted, the ServiceWorker will only be registered once the app
-   *     stabilizes.
+   *     `<timeout>` is required. Without it, the ServiceWorker is registered immediately
+   *     instead of waiting for the application to stabilize.
    * - `registerImmediately`: Register immediately.
    * - `registerWithDelay:<timeout>`: Register with a delay of `<timeout>` milliseconds. For
    *     example, use `registerWithDelay:5000` to register the ServiceWorker after 5 seconds. If