Update contributing guidelines (#2726)

* Update introduction_to_contributing.rst

* order/formatting

* typos

* Update introduction_to_contributing.rst

* Apply suggestions from code review

Co-authored-by: Cliff Hansen <cwhanse@sandia.gov>

* formatting, whatsnew, section reference

* fix section reference link in whatsnew

* Update introduction_to_contributing.rst

* forgot to delete "significant" somehow?

---------

Co-authored-by: Cliff Hansen <cwhanse@sandia.gov>

Author: RDaxini

docs/sphinx/source/contributing/introduction_to_contributing.rst

@@ -12,6 +12,27 @@ contributors from novice to expert. Don't worry if you don't (yet)
 understand parts of it.
 
 
+.. _core-guidelines:
+
+Core guidelines
+~~~~~~~~~~~~~~~
+While we welcome new contributors, reviewer capacity is limited. Therefore,
+following these core guidelines is essential:
+
+* Pull requests (PRs) should address one or more open issues. Context should
+  be provided, e.g. a link to the relevant discussion.
+* GSoC: For Google Summer of Code, we invite applications only from those with
+  PV modeling experience and who are motivated to join the pvlib maintenance
+  team.
+* pvlib-python is an advanced scientific modeling toolbox. A background
+  in solar energy and/or experience in pvlib-python is required to
+  address some issues effectively. It is not always clear which issues
+  fall into this bucket. Don't be offended if maintainers close your PR for
+  this reason.
+* Maintainers reserve the right to close PRs that do not comply with the
+  contributing guidelines.
+
+
 .. _easy-ways-to-contribute:
 
 Easy ways to contribute

docs/sphinx/source/whatsnew/v0.15.1.rst

@@ -59,6 +59,8 @@ Documentation
 * Fix a broken docstring reference to ``grounddiffuse`` in
   :py:func:`pvlib.irradiance.poa_components`
   (:issue:`2089`, :pull:`2708`)
+* Add :ref:`core-guidelines` to the :ref:`introduction-to-contributing` page.
+  (:issue:`2716`, :pull:`2726`)
 
 
 Testing