fix: add arn to outputs

Author: ckappen

outputs.tf

@@ -1,3 +1,8 @@
+output "arn" {
+  description = "The cloudwatch log group ARN"
+  value       = aws_cloudwatch_log_group.main.arn
+}
+
 output "name" {
   description = "The cloudwatch log group name"
   value       = aws_cloudwatch_log_group.main.name