docs(api): liquid classes in 8.5 (#18619)

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# Overview

Liquid classes in API 2.24. Includes new articles covering liquid
classes and liquid class definitions, plus changes throughout our
Complex Commands section.


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## Test Plan and Hands on Testing

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## Changelog
-brought over liquid classes text from [PR
#17992](https://github.com/Opentrons/opentrons/pull/17992/files#diff-0f90fc8fd15163b9fb8b128ac3c358036fbb7bef07c549fbdbec8b45cb26af51)
- reorganized the liquid classes article to ease into property
descriptions
- build issues with images in the properties table; currently in the
docs as a list to avoid this.
- adding custom liquid class creator section (and differentiate between
customizing and *creating* from scratch)
- built out liquid class definition tables section 
- updated API reference for tip handling options, `get_liquid_class` and
`define_liquid_class` entries
- linked users to github schema for creating their own liquid class 

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Co-authored-by: Edward Cormany <[email protected]>

Author: emilyburghardt