Rename exercises dir

Name it instead "topics" so it won't be
strange if some topics included "exercises" directory.

topics/aws/exercises/elastic_beanstalk_simple/exercise.md

@@ -0,0 +1,18 @@
+## AWS Elastic Beanstalk - Node.js
+
+### Requirements
+ 
+1. Having a running node.js application on AWS Elastic Beanstalk platform
+ 
+### Objectives
+
+1. Create an AWS Elastic Beanstalk application with the basic properties
+a. No ALB, No Database, Just use the default platform settings
+
+### Out of scope
+
+1. Having ALB attached in place
+2. Having custom domain name in place
+3. Having automated pipelines in place
+4. Having blue-green deployment in place
+5. Writing the Node.js application