Description

This PR adds the beginning of a time-focused chapter as part of addressing #25 .

Thanks for any thoughts or feedback you may have!

What is the nature of your change?

[x] Content additions or updates (adds or updates content)
[ ] Bug fix (fixes an issue).
[ ] Enhancement (adds functionality).
[ ] Breaking change (these changes would cause existing functionality to not work as expected).

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[x] I have read the CONTRIBUTING.md guidelines.
[x] My code follows the style guidelines of this project.
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[ ] I have made corresponding changes to related documentation (outside of book content).
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[x] New and existing tests pass locally with my changes.
[ ] I have added tests that prove my additions are effective or that my feature works.
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