Feature request: description string for my Chalice app

I would like to specify the `description` (in API Gateway) of my Chalice app in the [config file](https://aws.github.io/chalice/topics/configfile.html).

I can specify this manually in the AWS console by visiting API Gateway settings [1], and setting
`General settings` > `description`.

This unfortunately gets erased each time I `chalice deploy`.

How can I specify this permanently?

[1] https://console.aws.amazon.com/apigateway/home?region=us-east-1#/apis/{my_api_id}/settings

Start with the Chalice config file documentation and the API Gateway settings referenced in the issue. Trace how `chalice deploy` configures the API description; done means a description supplied in the config remains set after deployment.

Written by the indexing model from the issue text.