Resolve "Add an APD readout noise model"

Merge request check list

This is just a reminder about the most common mistakes. Please make sure that you tick all appropriate boxes. But please read our contribution guide at least once, it will save you unnecessary review cycles !

If an item doesn't apply to your merge request, check it anyway to make it apparent that there's nothing to do.

• Closes issue #416 (closed)
• Added tests for change code
• Updated documentation for changed code
• Documentation .rst files is written using semantic newlines
• User visible changes (including notable bug fixes and possible deprecations) are documented in CHANGELOG.rst
• Passes in this order
  • isort .
  • black .
  • blackdoc .
  • mypy .
  • flake8 .

If you have any questions of the points above, just submit and ask! This checklist is here to help you, not to deter you from contributing !