[Feature] Add extra SNS Subscription types: Get alerts for SMS (text) and/or https (webhooks) too

[Cameronsplaze]

Is your feature request related to a problem? Please describe.
I did email first because it was easy/cheap, and got us off the ground. Now that the project is farther along and we know what exactly we alert, look into supporting more than just email.

• Text would be nice, but since you have to rent a number, might cost a lot. It's possible you can't use cdk because of that too. I haven't looked into it really yet, so it'll require research.
• I feel like https wouldn't cost much, and might mean support for people to add to a discord server and not need to get all their friends numbers/emails for alerts then.

Describe the solution you'd like
If cheap, both SNS and https protocol options added for support.

Describe alternatives you've considered
Just keep it as is, email is "good enough". Seems like this could be very useful for people, without adding really any complexity to the code-base though.

Additional context

• SNS Subscription CDK docs