Update sphinx docs; use exhale and breathe.

docs/sphinx/resources.rst

@@ -0,0 +1,21 @@
+.. _resources:
+
+Resources
+=========
+
+This is a collection of useful documents for things.
+
+Quaternions
+-----------
+
++ As usual, `3Blue1Brown <https://www.3blue1brown.com/>`_ has a `good set
+  of videos <https://eater.net/quaternions>`_ on the subject.
++ `Intro to Quaternions <https://www.youtube.com/watch?v=fKIss4EV6ME>`_ is
+  another great video tutorial.
++ `Quaternions and Rotations <http://graphics.stanford.edu/courses/cs348a-17-winter/Papers/quaternion.pdf>`_
+  is a set of useful class notes.
++ `Understanding Quaternions <http://www.chrobotics.com/library/understanding-quaternions>`_
+  and
+  `Understanding Euler Angles <http://www.chrobotics.com/library/understanding-euler-angles>`_
+  approaches quaternions from the standpoint of attitude and orientation.
+