Add documentation on React Query standards and best practices

[theodur]

Description

With the migration to React Query for asynchronous state management in the app, the current Redux documentation will need to be replaced with best practices for using React Query. This should encompass documenting the new directory structure, patterns on creating/using queries and mutations, patterns on testing, when to use it vs Redux, etc.

Acceptance criteria

• Add documentation for React Query standards and best practices
• Remove irrelevant Redux documentation