Support an Alexa Verification action

**Is your feature request related to a problem? Please describe.**
When building Alexa skills, there's boilerplate code you use to verify the request coming in is valid. It can be run before your code and would make a great action step in a workflow.

Here's an example one I built in OpenWhisk (https://www.raymondcamden.com/2017/08/18/an-openwhisk-package-for-alexa-verification). OpenWhisk supports sequences, like pipedream workflows, and I used it in Alexa skills I went public with.

**Describe the solution you'd like**
It would just do the verification crap.

**Do you have a workaround?**
I could do it in a custom Node.js script.