chore(aws-cdk-readme): replace deprecated method used in aws-chatbot …

…README.md

Currently addLambdaInvokeCommandPermissions method used to get the permissions,
which is a deprecated method now.
Use addToPolicy method to get necessary permissions.

packages/@aws-cdk/aws-chatbot/README.md

@@ -27,17 +27,21 @@ This module is part of the [AWS Cloud Development Kit](https://github.com/aws/aw
 
 ```ts
 import * as chatbot from '@aws-cdk/aws-chatbot';
+import * as lambda from '@aws-cdk/aws-lambda';
 
 const slackChannel = new chatbot.SlackChannelConfiguration(this, 'MySlackChannel', {
   slackChannelConfigurationName: 'YOUR_CHANNEL_NAME',
   slackWorkspaceId: 'YOUR_SLACK_WORKSPACE_ID',
   slackChannelId: 'YOUR_SLACK_CHANNEL_ID',
 });
 
-slackChannel.addLambdaInvokeCommandPermissions();
-slackChannel.addNotificationPermissions();
-slackChannel.addSupportCommandPermissions();
-slackChannel.addReadOnlyCommandPermissions();
+const invokeCommandStatement = new iam.PolicyStatement({
+  effect: iam.Effect.ALLOW,
+  resources: ['RESOURCE_ARNS_ALLOWED'],
+  actions: ['INVOKING_ACTION_ALLOWED'],
+});
+
+slackChannel.addToRolePolicy(invokeCommandStatement);
 
 slackChannel.addToPrincipalPolicy(new iam.PolicyStatement({
   effect: iam.Effect.ALLOW,
@@ -46,6 +50,13 @@ slackChannel.addToPrincipalPolicy(new iam.PolicyStatement({
   ],
   resources: ['arn:aws:s3:::abc/xyz/123.txt'],
 }));
+
+const lambdaFn = new lambda.Function(this, 'MyChatbotHandler', {
+  code: lambda.Code.fromAsset('./code'),
+  runtime: lambda.Runtime.NODE_JS_14_X,
+  handler: 'FILE_NAME.handler',
+});
+lambdaFn.grantInvoke(slackChannel.role)
 ```
 
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