DocFlags: Change field init type from str to int

[leroyvn]

Description

Closes #356.

This PR fixes an issue where an incorrect flag field type would raise a TypeError on Python 3.11.

Checklist

• The code follows the relevant coding guidelines
• The code generates no new warnings
• The code is appropriately documented
• The code is tested to prove its function
• The feature branch is rebased on the current state of the main branch
• I updated the change log if relevant
• I give permission that the Eradiate project may redistribute my contributions under the terms of its license

[leroyvn]

Docs build here; check that class docstrings are assembled correctly.

[leroyvn]

Everything is fine, let's merge this.