Adds example showing how to chunk over data

[skrawcz]

This example shows how one might use Hamilton in
a for loop to chunk over data. It is very contrived,
but I think illustrates the point.

Additions

• hello world chunked example

Testing

1. works locally!

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows the standards laid out in the TODO link to standards
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

Testing checklist

Python

- [] python 3.6

• python 3.7

[skrawcz]

Not going to add this -- will rethink this example a little -- probably not worth the code for the example.