Add top level module docstring to orient new user

I like how modules provide some basic documentation
or at least pointers when I do something like
"numpy?" in the IPython shell.

Author: yarikoptic

dandi/__init__.py

@@ -1,3 +1,18 @@
+"""
+DANDI
+=====
+
+The `dandi <https://github.com/dandi/dandi-cli>`_ library provides both a
+command line interface (CLI) and a Python API for interacting with `DANDI
+Archive <https://dandiarchive.org>`_.
+
+Additional references:
+
+- `Source Git repository <https://github.com/dandi/dandi-cli>`_
+- `Library documentation <https://dandi.readthedocs.io/>`_
+- `DANDI Archive handbook <https://www.dandiarchive.org/handbook/>`_
+"""
+
 import logging
 import os