Users can add a lambda function to the resource list in their Sam template to reduce errors in template configuration

Once a user has iterated on their lambda function and is happy with it, they may want a convenient way to produce an initial sam template resource that references this function. This becomes more useful as the toolkit adds actions that operate on sam templates and sam template resources.

Prompting for resource name and runtime, it should be possible to auto-generate:

```yaml
SOME_RESOURCE_NAME:
Type: AWS::Serverless::Function
Properties:
CodeUri: APPROPRIATE_LOCATION/
Handler: APPROPRIATE_HANDLER
Runtime: APPROPRIATE_RUNTIME
```

Acceptance Criteria:
* user has a way to produce sam template resource definition for a function of interest

Start by locating the toolkit entry points for Lambda functions and SAM template resources, then trace how existing template actions prompt users and update templates. The issue calls for a way to prompt for a resource name and runtime and produce an AWS::Serverless::Function definition; done means that resource can be generated for a function of interest without manual configuration.

Written by the indexing model from the issue text.