Add row_factories import to __init__

[leorudczenko]

Summary

This merge request fixes a small issue which helps code editors to provide productivity improvements for etlhelper.row_factories.

Description

Currently, etlhelper.row_factories is accessed directly from etlhelper/row_factories.py, it is not imported in any __init__ files. Whilst the submodule is accessible, code editors (e.g., VSCode) cannot provide productivity improvements for this submodule:

To solve this, the following has been done:

• Add from etlhelper import row_factories to etlhelper/__init__.py

[volcan01010]

This works nicely. It's a small addition and not breaking anything, so I'll merge into main instead.