doc: Added more doc

LoopWithCsv.yaml

@@ -1,10 +1,10 @@
 schemaVersion: '0.3'
 mainSteps:
+  # ssm parameter supports StringList, which is comma separated strings (i.e. 111111111111,222222222222)
   - name: GetParameter
     action: aws:executeAwsApi
     nextStep: ConvertInputToList
     isEnd: false
-    # parameter contains comma separated ids (i.e. 111111111111,222222222222)
     inputs:
       Service: ssm
       Api: GetParameter
@@ -13,7 +13,8 @@ mainSteps:
       - Name: Accounts
         Selector: $.Parameter.Value
         Type: String
-  # input needs to be transformed to a list of string in order to be used by aws:loop
+  # The so-called StringList needs to be transformed to a list[str] in order to be used by aws:loop
+  # There is no native action for that, and I need to use python
   - name: ConvertInputToList
     action: aws:executeScript
     nextStep: Loop