Add Preferences library API and tutorial documents (espressif#6442)

* Add Preferences library API and tutorial documents

Add API and tutorial documents for the  Preferences library.

* Revise per review

Correct some errors. Remove the "wordiness" is a few places.

* Correct link to Preferences API

Update the references and link to the Preferences API document.

Co-authored-by: Pedro Minatel <[email protected]>
Co-authored-by: Me No Dev <[email protected]>

Author: 3 people