Update outdated nbviewer links (#1726)

* Broken links

Fixes : #1721

Signed-off-by: kshitiz305 <kshitiz305@live.com>

* move whatsnew entry to Documentation section

* add 0.9.6 whatsnew to whatsnew index

---------

Signed-off-by: kshitiz305 <kshitiz305@live.com>
Co-authored-by: Kevin Anderson <kevin.anderso@gmail.com>

Author: kshitiz305

docs/sphinx/source/index.rst

@@ -19,7 +19,7 @@ Please see the :ref:`installation` page for installation help.
 
 For examples of how to use pvlib python, please see
 :ref:`package_overview` and our `Jupyter Notebook tutorials
-<http://nbviewer.ipython.org/github/pvlib/pvlib-python/tree/main/docs/
+<http://nbviewer.org/github/pvlib/pvlib-python/tree/main/docs/
 tutorials/>`_. The documentation assumes general familiarity with
 Python, NumPy, and Pandas. Google searches will yield many
 excellent tutorials for these packages.
@@ -74,7 +74,7 @@ Additional pvlib python publications include:
   (`paper
   <https://github.com/pvlib/pvsc2015/blob/main/pvlib_pvsc_42.pdf>`__ and
   the `notebook to reproduce the figures
-  <http://nbviewer.ipython.org/github/pvlib/pvsc2015/blob/main/paper.ipynb>`_)
+  <http://nbviewer.org/github/pvlib/pvsc2015/blob/main/paper.ipynb>`_)
 * J.S. Stein, W.F. Holmgren, J. Forbess, and C.W. Hansen,
   "PVLIB: Open Source Photovoltaic Performance Modeling Functions
   for Matlab and Python," in 43rd Photovoltaic Specialists Conference, 2016.

docs/sphinx/source/whatsnew.rst

@@ -6,6 +6,7 @@ What's New
 
 These are new features and improvements of note in each release.
 
+.. include:: whatsnew/v0.9.6.rst
 .. include:: whatsnew/v0.9.5.rst
 .. include:: whatsnew/v0.9.4.rst
 .. include:: whatsnew/v0.9.3.rst

docs/sphinx/source/whatsnew/v0.9.6.rst

@@ -26,6 +26,7 @@ Documentation
 ~~~~~~~~~~~~~
 * Updated the description of the interval parameter in
   :py:func:`pvlib.iotools.get_psm3`. (:issue:`1702`, :pull:`1712`)
+* Fixed outdated nbviewer links. (:issue:`1721`, :pull:`1726`)
 
 Benchmarking
 ~~~~~~~~~~~~~
@@ -39,3 +40,6 @@ Contributors
 ~~~~~~~~~~~~
 * Adam R. Jensen (:ghuser:`adamrjensen`)
 * Siddharth Kaul (:ghuser:`k10blogger`)
+* Kshitiz Gupta (:ghuser:`kshitiz305`)
+* Stefan de Lange (:ghuser:`langestefan`)
+