Add biologist focused tutorials

[d33bs]

Description

This PR expands and adds notebooks to help with biologist-related understanding of this project's work. I've also updated the readme to more prominently feature these as a "first-stop" for folks interested in using CytoTable.

Closes #350

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• Bug fix (fixes an issue).
• Enhancement (adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• This change requires a documentation update.

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[gwaybio]

Great to see this progress! Most of my suggestions involve active voice, adding common language used in the field, and clarity improvements.

[d33bs]

Thanks @gwaybio ! Merging this in.