added back bootstrap step (#96)

Co-authored-by: Maish Saidel-Keesing

content/microservices/platform/tabs/cdk.md

@@ -9,6 +9,7 @@ hidden: true
 ```bash
 cd ~/environment/ecsdemo-platform/cdk
 pip install -r requirements.txt --user
+cdk bootstrap aws://$AWS_ACCOUNT_ID/$AWS_DEFAULT_REGION
 ```
 
 #### Confirm that the cdk can synthesize the assembly CloudFormation templates