Publish Stack Notifications with Message Attributes

## 1. Title
Publish Stack Notifications with Message Attributes

## 2. Scope of request
Often, I am only interested in notifications for certain resource types (or even just the stack itself and not individual resources). Currently, stack notifications are published to SNS without message attributes, so if I want to filter out messages, I have to write a Lambda to do that for me. If the stack/event notifications were published with message attributes, the lambda would not be needed and filtering could be setup on a subscription based on attribute value(s)

## 3. Expected behavior
SNS Stack / Event Notifications should be published with message attributes. Attributes that would be useful include:
- StackName / StackId
- ResourceType
- ResourceStatus
- LogicalResourceId

## 4. Suggest specific test cases
Event / Notification should have message attribute with name x and value y

## 5. Helpful Links to speed up research and evaluation
https://docs.aws.amazon.com/sns/latest/dg/sns-message-attributes.html
https://docs.aws.amazon.com/sns/latest/dg/sns-message-filtering.html

## 6. Category (required) - Will help with tagging and be easier to find by other users to +1
9. Integration (MQ, SQS, SNS,...)