Add API Ref for Projects

Closes #967

Author: sigmavirus24

docs/source/api-reference/projects.rst

@@ -0,0 +1,24 @@
+========================================
+ Projectss and their Associated Objects
+========================================
+
+This section of the documentation covers the representations of various
+objects related to the `Projects API`_.
+
+Project Objects
+---------------
+
+.. autoclass:: github3.projects.Project
+    :inherited-members:
+
+.. autoclass:: github3.projects.ProjectColumn
+    :inherited-members:
+
+.. autoclass:: github3.projects.ProjectCard
+    :inherited-members:
+
+
+.. ---
+.. links
+.. _Projects API:
+    https://docs.github.com/en/rest/reference/projects