Added stronger callouts for ScheduledEvent listener (#366)

* Added an aside about Scheduled event Listeners

Added an aside to create a stronger callout of this requirement that is easier to spot and reference than the background description.

* Added note in background about cron triggers

* Updated Desc language for accuracy and clarity

* Forgot a period

Author: sgraden

products/workers/src/content/platform/cron-triggers/index.md

@@ -12,6 +12,12 @@ Cron Triggers allow users to map a cron expression to a Worker script using a [S
 
 Cron Triggers can be added to scripts with the Cloudflare API, or in the dashboard on a [Workers Triggers tab](https://dash.cloudflare.com/?to=/:account/workers) up to the [per-script limit](/platform/limits). If a script is managed with Wrangler, Cron Triggers should be exclusively managed through the **`wrangler.toml`** file.
 
+<Aside header="Requires a ScheduledEvent Listener">
+
+In order to respond to a Cron Trigger, a [ScheduledEvent](/runtime-apis/scheduled-event) listener must be added to the Workers script. Similar to the Fetch listener, add your code within the Scheduled listener to specify what the Worker should do under the condition that it was triggered by a Cron Trigger.
+
+</Aside>
+
 ![workers-schedule-editor](./media/workers-schedule-editor.png)
 
 ## Supported cron expressions
@@ -67,4 +73,4 @@ Users can view the execution history of their Cron Triggers on the Past Events s
 
 Note: it can take up to 30 minutes before events are displayed in Past Events when creating a new Worker or changing a Worker's name.
 
-See [Metrics and Analytics](/learning/metrics-and-analytics) for more information.
+See [Metrics and Analytics](/learning/metrics-and-analytics) for more information.

products/workers/src/content/runtime-apis/scheduled-event.md

@@ -2,7 +2,8 @@
 
 ## Background
 
-The event type for Scheduled requests to a Worker. The `Object` passed through as `event` in [`addEventListener()`](/runtime-apis/add-event-listener).
+A ScheduledEvent is the event type for scheduled requests to a Worker. It is the `Object` passed through as the `event` when a Worker's `scheduled` [`addEventListener()`](/runtime-apis/add-event-listener) is invoked by a Worker's [Cron Trigger](/platform/cron-triggers).
+
 
 ## Context
 
@@ -34,4 +35,4 @@ When a Workers script is invoked by a [Cron Trigger](/platform/cron-triggers), t
 
     - Use this method to notify the runtime to wait for asynchronous tasks (e.g. logging, analytics to third-party services, streaming and caching). The first `event.waitUntil` to fail will be observed and recorded as the status in the [Cron Trigger](/platform/cron-triggers) Past Events table. Otherwise, it will be reported as a Success.
 
-</Definitions>
+</Definitions>