Update documentation to for all hooks and fix loading state examples

Documentation for 'frappe-react-sdk' mentions handling **loading state** if it _is validating_.
However, [SWR documnetation - Quick start](https://github.com/vercel/swr) suggests another method
that we've been already using all along. Also [this](https://github.com/vercel/swr/discussions/563) discussion clarifies the confusion.
**If you find it appropriate**, the documentation for this SDK can be amended as it returns similar states.

I hope this helps...Thank you!