question: a template for `webapp for containers`

when I create `webapp for containers` service from portal I am able to select a container image during creation. In the settings of this resource there is `docker container` section using which I can change the image if I want to. on normal `webapp app service` I don't see that `docker container` in settings section of normal `webapp` service.

please help in understanding what configuration should be added to `Microsoft.Web/sites` to make it a `webapp for containers` resource.

The issue names the Azure portal and the Microsoft.Web/sites resource, but no repository file, test, or template is identified. Start by determining the expected configuration for a container-based web app and where that template belongs; done means the required configuration is clearly documented or represented in a usable template.

Written by the indexing model from the issue text.