Support Google App Engine

[toyinswift]

Hey, Awesome library. please can you add support for CloudRun or Google App Engine?

I think it just requires an app.yaml file to set things up for Google app engine. or just add the following code to make it deployable on Cloud run

you can read more here
https://github.com/GoogleCloudPlatform/cloud-run-button

Thanks!