chore(scheduler-alpha): clean up readme (#32034)

small changes to README before developer preview, mostly formatting and some grammar fixes

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: gracelu0

packages/@aws-cdk/aws-scheduler-alpha/README.md

@@ -16,26 +16,26 @@
 <!--END STABILITY BANNER-->
 
 [Amazon EventBridge Scheduler](https://aws.amazon.com/blogs/compute/introducing-amazon-eventbridge-scheduler/) is a feature from Amazon EventBridge
-that allows you to create, run, and manage scheduled tasks at scale. With EventBridge Scheduler, you can schedule one-time or recurrently tens 
+that allows you to create, run, and manage scheduled tasks at scale. With EventBridge Scheduler, you can schedule one-time or recurrently tens
 of millions of tasks across many AWS services without provisioning or managing underlying infrastructure.
 
-1. **Schedule**: A schedule is the main resource you create, configure, and manage using Amazon EventBridge Scheduler. Every schedule has a schedule expression that determines when, and with what frequency, the schedule runs. EventBridge Scheduler supports three types of schedules: rate, cron, and one-time schedules. When you create a schedule, you configure a target for the schedule to invoke. 
-2. **Targets**: A target is an API operation that EventBridge Scheduler calls on your behalf every time your schedule runs. EventBridge Scheduler
-supports two types of targets: templated targets and universal targets. Templated targets invoke common API operations across a core groups of 
-services. For example, EventBridge Scheduler supports templated targets for invoking AWS Lambda Function or starting execution of Step Function state
+1. **Schedule**: A schedule is the main resource you create, configure, and manage using Amazon EventBridge Scheduler. Every schedule has a schedule expression that determines when, and with what frequency, the schedule runs. EventBridge Scheduler supports three types of schedules: rate, cron, and one-time schedules. When you create a schedule, you configure a target for the schedule to invoke.
+2. **Target**: A target is an API operation that EventBridge Scheduler calls on your behalf every time your schedule runs. EventBridge Scheduler
+supports two types of targets: templated targets and universal targets. Templated targets invoke common API operations across a core groups of
+services. For example, EventBridge Scheduler supports templated targets for invoking AWS Lambda Function or starting execution of Step Functions state
 machine. For API operations that are not supported by templated targets you can use customizable universal targets. Universal targets support calling
 more than 6,000 API operations across over 270 AWS services.
 3. **Schedule Group**: A schedule group is an Amazon EventBridge Scheduler resource that you use to organize your schedules. Your AWS account comes
-with a default scheduler group. A new schedule will always be added to a scheduling group. If you do not provide a scheduling group to add to, it 
-will be added to the default scheduling group. You can create up to 500 schedule groups in your AWS account. Groups can be used to organize the 
+with a default scheduler group. A new schedule will always be added to a scheduling group. If you do not provide a scheduling group to add to, it
+will be added to the default scheduling group. You can create up to 500 schedule groups in your AWS account. Groups can be used to organize the
 schedules logically, access the schedule metrics and manage permissions at group granularity (see details below). Scheduling groups support tagging:
 with EventBridge Scheduler, you apply tags to schedule groups, not to individual schedules to organize your resources.
 
 This module is part of the [AWS Cloud Development Kit](https://github.com/aws/aws-cdk) project. It allows you to define Event Bridge Schedules.
 
 > This module is in active development. Some features may not be implemented yet.
 
-## Defining a schedule 
+## Defining a schedule
 
 ```ts
 declare const fn: lambda.Function;
@@ -55,10 +55,12 @@ const schedule = new Schedule(this, 'Schedule', {
 
 ### Schedule Expressions
 
-You can choose from three schedule types when configuring your schedule: rate-based, cron-based, and one-time schedules. 
+You can choose from three schedule types when configuring your schedule: rate-based, cron-based, and one-time schedules.
 
-Both rate-based and cron-based schedules are recurring schedules. You can configure each recurring schedule type using a schedule expression. For 
-cron-based schedule you can specify a time zone in which EventBridge Scheduler evaluates the expression. 
+Both rate-based and cron-based schedules are recurring schedules. You can configure each recurring schedule type using a schedule expression.
+
+For
+cron-based schedules you can specify a time zone in which EventBridge Scheduler evaluates the expression.
 
 ```ts
 declare const target: targets.LambdaInvoke;
@@ -82,7 +84,7 @@ const cronBasedSchedule = new Schedule(this, 'Schedule', {
 });
 ```
 
-A one-time schedule is a schedule that invokes a target only once. You configure a one-time schedule when by specifying the time of the day, date, 
+A one-time schedule is a schedule that invokes a target only once. You configure a one-time schedule by specifying the time of day, date,
 and time zone in which EventBridge Scheduler evaluates the schedule.
 
 ```ts
@@ -100,13 +102,13 @@ const oneTimeSchedule = new Schedule(this, 'Schedule', {
 
 ### Grouping Schedules
 
-Your AWS account comes with a default scheduler group. You can access default group in CDK with:
+Your AWS account comes with a default scheduler group. You can access the default group in CDK with:
 
 ```ts
 const defaultGroup = Group.fromDefaultGroup(this, "DefaultGroup");
 ```
 
-If not specified a schedule is added to the default group. However, you can also add the schedule to a custom scheduling group managed by you:
+You can add a schedule to a custom scheduling group managed by you. If a custom group is not specified, the schedule is added to the default group.
 
 ```ts
 declare const target: targets.LambdaInvoke;
@@ -154,13 +156,18 @@ new Schedule(this, 'Schedule', {
 ## Scheduler Targets
 
 The `@aws-cdk/aws-scheduler-targets-alpha` module includes classes that implement the `IScheduleTarget` interface for
-various AWS services. EventBridge Scheduler supports two types of targets: templated targets invoke common API
-operations across a core groups of services, and customizable universal targets that you can use to call more
-than 6,000 operations across over 270 services. A list of supported targets can be found at `@aws-cdk/aws-scheduler-targets-alpha`. 
+various AWS services. EventBridge Scheduler supports two types of targets:
+
+1. **Templated targets** which invoke common API
+operations across a core groups of services, and
+2. **Universal targets** that you can customize to call more
+than 6,000 operations across over 270 services.
+
+A list of supported targets can be found at `@aws-cdk/aws-scheduler-targets-alpha`.
 
-### Input 
+### Input
 
-Target can be invoked with a custom input. Class `ScheduleTargetInput` supports free form text input and JSON-formatted object input:
+Targets can be invoked with a custom input. The `ScheduleTargetInput`class supports free-form text input and JSON-formatted object input:
 
 ```ts
 const input = ScheduleTargetInput.fromObject({
@@ -182,14 +189,14 @@ const text = `Attempt number: ${ContextAttribute.attemptNumber}`;
 const input = ScheduleTargetInput.fromText(text);
 ```
 
-### Specifying Execution Role 
+### Specifying an execution role
 
 An execution role is an IAM role that EventBridge Scheduler assumes in order to interact with other AWS services on your behalf.
 
 The classes for templated schedule targets automatically create an IAM role with all the minimum necessary
 permissions to interact with the templated target. If you wish you may specify your own IAM role, then the templated targets
-will grant minimal required permissions. For example: for invoking Lambda function target `LambdaInvoke` will grant
-execution IAM role permission to `lambda:InvokeFunction`.
+will grant minimal required permissions. For example, the target `LambdaInvoke` will grant the
+IAM execution role `lambda:InvokeFunction` permission to invoke the Lambda function.
 
 ```ts
 declare const fn: lambda.Function;
@@ -206,14 +213,14 @@ const target = new targets.LambdaInvoke(fn, {
 });
 ```
 
-### Specifying Encryption key
+### Specifying an encryption key
 
-EventBridge Scheduler integrates with AWS Key Management Service (AWS KMS) to encrypt and decrypt your data using an AWS KMS key. 
+EventBridge Scheduler integrates with AWS Key Management Service (AWS KMS) to encrypt and decrypt your data using an AWS KMS key.
 EventBridge Scheduler supports two types of KMS keys: AWS owned keys, and customer managed keys.
 
-By default, all events in Scheduler are encrypted with a key that AWS owns and manages. 
-If you wish you can also provide a customer managed key to encrypt and decrypt the payload that your schedule delivers to its target using the `key` property. 
-Target classes will automatically add AWS KMS Decrypt permission to your schedule's execution role permissions policy.
+By default, all events in Scheduler are encrypted with a key that AWS owns and manages.
+If you wish you can also provide a customer managed key to encrypt and decrypt the payload that your schedule delivers to its target using the `key` property.
+Target classes will automatically add AWS `kms:Decrypt` permission to your schedule's execution role permissions policy.
 
 ```ts
 declare const key: kms.Key;
@@ -251,7 +258,7 @@ const schedule = new Schedule(this, 'Schedule', {
 
 > Visit [Configuring flexible time windows](https://docs.aws.amazon.com/scheduler/latest/UserGuide/managing-schedule-flexible-time-windows.html) for more details.
 
-## Error-handling 
+## Error-handling
 
 You can configure how your schedule handles failures, when EventBridge Scheduler is unable to deliver an event
 successfully to a target, by using two primary mechanisms: a retry policy, and a dead-letter queue (DLQ).
@@ -280,10 +287,10 @@ const target = new targets.LambdaInvoke(fn, {
 
 ## Monitoring
 
-You can monitor Amazon EventBridge Scheduler using CloudWatch, which collects raw data 
-and processes it into readable, near real-time metrics. EventBridge Scheduler emits 
+You can monitor Amazon EventBridge Scheduler using CloudWatch, which collects raw data
+and processes it into readable, near real-time metrics. EventBridge Scheduler emits
 a set of metrics for all schedules, and an additional set of metrics for schedules that
-have an associated dead-letter queue (DLQ). If you configure a DLQ for your schedule, 
+have an associated dead-letter queue (DLQ). If you configure a DLQ for your schedule,
 EventBridge Scheduler publishes additional metrics when your schedule exhausts its retry policy.
 
 ### Metrics for all schedules