Enhance documentation for contributing new checks

[bendichter]

• Added a new guide on contributing checks to NWBInspector in contributing_checks.rst.
• Updated developer_guide.rst to reference the new contributing checks guide.
• Modified .gitignore to exclude additional build artifacts.

This update aims to streamline the contribution process and improve clarity for new contributors.

[stephprince]

looks great!

[stephprince]

Suggested change

	3. Link to relevant :doc:`best practices documentation <best_practices/best_practices_index>`
	3. Link to relevant :doc:`best practices documentation <best_practices/best_practices_index>` if applicable. If proposing a new best practice, please describe in detail.

[stephprince]

Suggested change

	10. ``_image_series.py`` - :py:class:`~pynwb.image.ImageSeries` objects
	10. ``_image_series.py`` - :py:class:`~pynwb.image.ImageSeries` objects
	11. ``_images.py`` - :py:class:`~pynwb.base.Images` objects
	12. ``_general.py`` - attributes of general neurodata types

[stephprince]

Suggested change

	:doc:`how to contribute new checks <contributing_checks>`. A guideline on how to build a new data interface and a graphical
	overview of the object structure can be found in our primary :nwbinspector-contributing:`Contributing <>` page.
	:doc:`how to contribute new checks <contributing_checks>`.

The "Contributing" page is now a bit repetitive with the new contributing_checks.rst documentation, and I think "Contributing" should be more generalized than just adding a new check. Your proposed documentation is also probably easier for new contributors to find.

What do you think about making CONTRIBUTING.md focused on coding style and the code of conduct, and then moving any other "Adding a new check" information from CONTRIBUTING.md to contributing_checks.rst.

[stephprince]

Suggested change

	4. Choose the Right Importance Level
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	.. note::
	The function name for the check should always start with ``check_``
	4. Choose the Right Importance Level
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[stephprince]

Suggested change

	6. Best Practices for Check Implementation
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	1. Keep logic simple and focused
	2. Use descriptive variable names
	3. Add comments for complex logic
	4. Reuse utility functions from :doc:`api/utils` when possible
	5. Make error messages clear and actionable
	6. Include links to relevant documentation in docstrings
	7. Submit Your PR
	^^^^^^^^^^^^^^^^^
	6. Add Check to the Public Interface
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	1. Add an import for your check from the appropriate module in ``src/nwbinspector/checks/__init__.py``
	2. Add your check to the ```__all__``` list in ``src/nwbinspector/checks/__init__.py`` to indicate
	the check is part of the public interface.
	7. Add Check to the Documentation
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	Add a link to your new check function in the relevant best practice section of the ``docs/best_practices`` folder.
	If needed, add a new section and label for your check:
	.. code-block:: rst
	.. _best_practice_my_feature:
	My Feature
	~~~~~~~~~~
	Description of the best practice.
	Check function: :py:meth:`~nwbinspector.checks._tables.check_my_feature`
	.. note::
	If the best practice label in the ``.rst`` file ends with the same pattern as the check function name,
	(e.g. ``.. _best_practice_my_feature:`` and ``check_my_feature``), a link to the best practice documentation
	will be automatically added to the function API documentation.
	However, if the name of your check function does not match the name of your best practice section label
	(e.g. if a single best practices section has multiple check functions), you can include a link in the function
	docstring to link to the related best practice section.
	.. code-block:: python
	def check_my_feature(nwbfile: NWBFile) -> Optional[InspectorMessage]:
	"""
	One-line description of what this check validates.
	Best Practice: :ref:`best_practice_my_feature_unique_label`
	"""
	7. Best Practices for Check Implementation
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	1. Keep logic simple and focused
	2. Use descriptive variable names
	3. Add comments for complex logic
	4. Reuse utility functions from :doc:`api/utils` when possible
	5. Make error messages clear and actionable
	6. Include links to relevant documentation in docstrings
	8. Submit Your PR
	^^^^^^^^^^^^^^^^^

I came across this documentation docstring behavior recently and thought it might be helpful to describe here. This description is based on my understanding of the conf.py file, but feel free to update if I'm missing anything:

nwbinspector/docs/conf.py

Lines 70 to 72 in e6ea845

	def add_refs_to_docstrings(app, what, name, obj, options, lines):
	if what == "function" and obj.__name__.startswith("check_") and "Best Practice: " not in obj.__doc__:
	lines.append(f"Best Practice: :ref:`best_practice_{obj.__name__.split('check_')[1]}`")