basic-sdk example

[greenwoodcm]

adds an example for a basic Lambda function that calls S3. this demonstrates the best practice of instantiating an SDK client during function initialization (main method) and reusing that client across multiple invokes.

Issue #, if available:
#616

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• I confirm that my contribution is made under the terms of the Apache 2.0 license.
• I confirm that I've made a best effort attempt to update all relevant documentation.

[bnusunny]

Could you add a simple README file?

[timClicks]

Is it possible to add a README to the example to make it obvious that arguments need to be passed when calling it?

// This example requires the following input to succeed:
// { "bucket": "bucket-to-list" }

(I know that the other examples don't have thorough READMEs, but it would be worthwhile practice to start)

[greenwoodcm]

added a README in the latest