Add getting started doc for dev environment

also change docs theme

docs/index.rst

@@ -4,6 +4,10 @@ Tailbone
 
 Welcome to Tailbone, part of the Rattail project.
 
+..
+   While the core Rattail package provides the data schema / ORM / application
+   layer, the Tailbone package provides the web application layer.
+
 The documentation you are currently reading is for the Tailbone web application
 package.  Some additional information is available on the `website`_.  Clearly
 not everything is documented yet.  Below you can see what has received some
@@ -11,6 +15,13 @@ attention thus far.
 
 .. _website: https://rattailproject.org/
 
+Getting Started:
+
+.. toctree::
+   :maxdepth: 1
+
+   devenv
+
 Narrative Documentation:
 
 .. toctree::