add an option to return fields on update

[evstratbg]

Added a returning method for UpdateQuery to get an option to fetch changed data

Description

This change

Motivation and Context

I faced a need, to get some data from updated rows. It looks like related to this issue

How Has This Been Tested?

Tested locally by adding res = await Users(company_id=self. company_id).update(is_active=0).returning('id')

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added the changelog accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

I understand, that this is

1. a breaking change
2. maybe not the best way to put

but I really want this feature so help me know where to implement it better

[long2ice]

Thanks! Please add some tests and update changelog. Also the syntax is just for postgres, right?