change(doc): Document how to add a column family

[teor2345]

Motivation

This PR documents how to add a new column family. (Or convert old column families to be type-safe.)

Close #7833

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Solution

• Document how to add a new column family
• Document how to read from a column family
• Document how to write batches to a column family and write a batch to the database
• Link to code examples

Review

This is a routine documentation update.

Reviewer Checklist

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[arya2]

Looks good!