Adds documentation showing scalar creation & input

[skrawcz]

Functions can create or take in scalars. Adding this to the
example so that people can see that more explicitly.

Additions

• example showing Hamilton using scalars.

Removals

• N/A

Changes

• N/A

Testing

1. Tested 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 developer setup guide
• 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