Create alarms only on defined stages

[ZaneGeiser]

Hi,

I wanted to add support so that the alarms could only be created on specific stages.

Simply put if you define stages in the config then the alarms will only get created when the current stage is in the list.
If stages is not defined at all, then the alarms still get created.

custom:
    sqs-alarms:
        stages:
            - prod

If you are happy with the changes then I can add the new feature to the README.

Thanks!

[ZaneGeiser]

Hi @sbstjn,
What do you think about adding this as a new feature?