Add S3 bucket naming conventions to description

I forgot about naming conventions when I created my bucket name, even though I added an `AllowedPattern`, I don't get validation on the form.

Author: illusional

src/templates/cromwell/cromwell-aio.template.yaml

@@ -66,8 +66,13 @@ Parameters:
     Description: "Choose the two Availability Zones to deploy instances for AWS Batch."
     Type: List<AWS::EC2::AvailabilityZone::Name>
   S3BucketName:
-    Description: A S3 bucket name for storing analysis results
+    Description: >-
+      A S3 bucket name for storing analysis results. 
+      The bucket name must respect the S3 bucket naming conventions 
+      (can contain lowercase letters, numbers, periods and hyphens).
     Type: String
+    AllowedPattern: "(?=^.{3,63}$)(?!^(\\d+\\.)+\\d+$)(^(([a-z0-9]|[a-z0-9][a-z0-9\\-]*[a-z0-9])\\.)*([a-z0-9]|[a-z0-9][a-z0-9\\-]*[a-z0-9])$)"
+    ConstraintDescription: "Must respect S3 bucket naming conventions"
   ExistingBucket:
     Description: Does this bucket already exist?
     Type: String
@@ -218,4 +223,4 @@ Outputs:
     Value: !GetAtt 'GenomicsWorkflowStack.Outputs.GenomicsEnvHighPriorityJobQueueArn'
     Description: >-
       AWS Batch job queue for high priority workflow jobs, based on EC2 On-Demand
-      instances
+      instances