Add custom resource examples

In `aws/solutions`, we are removing the existing examples since they are out of date and have native ways to do the same thing in CloudFormation without a custom resource.

Add a simple Python and JavaScript example to show how to create a custom resource and respond to events from CloudFormation using cfn-response.

Review the examples in aws/solutions and the CloudFormation custom-resource event flow first, then check the cfn-response usage described in the issue. Done means the outdated examples are replaced with simple Python and JavaScript examples that create a custom resource and respond to CloudFormation events.

Written by the indexing model from the issue text.