chore(eks): updated the eks launch template support topic in the docs

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

@@ -232,8 +232,40 @@ cluster.addNodegroupCapacity('extra-ng-spot', {
 
 #### Launch Template Support
 
-You can specify a launch template that the node group will use. Note that when using a custom AMI, Amazon EKS doesn't merge any user data.
-Rather, You are responsible for supplying the required bootstrap commands for nodes to join the cluster.
+You can specify a launch template that the node group will use. For example, this can be useful if you want to use
+a custom AMI or add custom user data.
+
+When supplying a custom user data script, it must be encoded in the MIME multi-part archive format, since Amazon EKS merges with its own user data. Visit the [Launch Template Docs](https://docs.aws.amazon.com/eks/latest/userguide/launch-templates.html#launch-template-user-data)
+for mode details.
+
+```ts
+const userData = `MIME-Version: 1.0
+Content-Type: multipart/mixed; boundary="==MYBOUNDARY=="
+
+--==MYBOUNDARY==
+Content-Type: text/x-shellscript; charset="us-ascii"
+
+#!/bin/bash
+echo "Running custom user data script"
+
+--==MYBOUNDARY==--\\
+`;
+const lt = new ec2.CfnLaunchTemplate(this, 'LaunchTemplate', {
+  launchTemplateData: {
+    instanceType: 't3.small',
+    userData: Fn.base64(userData),
+  },
+});
+cluster.addNodegroupCapacity('extra-ng', {
+  launchTemplateSpec: {
+    id: lt.ref,
+    version: lt.attrLatestVersionNumber,
+  },
+});
+
+```
+
+Note that when using a custom AMI, Amazon EKS doesn't merge any user data. Which means you do not need the multi-part encoding. and are responsible for supplying the required bootstrap commands for nodes to join the cluster.
 In the following example, `/ect/eks/bootstrap.sh` from the AMI will be used to bootstrap the node.
 
 ```ts
@@ -245,19 +277,19 @@ userData.addCommands(
 const lt = new ec2.CfnLaunchTemplate(this, 'LaunchTemplate', {
   launchTemplateData: {
     imageId: 'some-ami-id', // custom AMI
-    instanceType: new ec2.InstanceType('t3.small').toString(),
+    instanceType: 't3.small',
     userData: Fn.base64(userData.render()),
   },
 });
 cluster.addNodegroupCapacity('extra-ng', {
   launchTemplateSpec: {
     id: lt.ref,
-    version: lt.attrDefaultVersionNumber,
+    version: lt.attrLatestVersionNumber,
   },
 });
 ```
 
-You may specify one or instance types in either the `instanceTypes` property of `NodeGroup` or in the launch template, **but not both**.
+You may specify one `instanceType` in the launch template or multiple `instanceTypes` in the node group, **but not both**.
 
 > For more details visit [Launch Template Support](https://docs.aws.amazon.com/eks/latest/userguide/launch-templates.html).