Add links to repo, Docker Hub, and license to Sphinx doc index

doc/index.rst

@@ -14,6 +14,11 @@ Introduction
 =============
 Welcome to the DORiE Documentation!
 
+DORiE is a DUNE module for solving the Richards equation. The source code is
+available from the `public repository <https://ts-gitlab.iup.uni-heidelberg.de/dorie/dorie>`_.
+A ready-to-use application is available from `Docker Hub <https://hub.docker.com/r/dorie/dorie/>`_.
+DORiE is licensed under the `MIT License <https://ts-gitlab.iup.uni-heidelberg.de/dorie/dorie/blob/master/LICENSE.md>`_.
+
 Never used DORiE before? Get to learn its features by working through :ref:`quickstart`.
 If you have already installed DORiE, jump straight to the :doc:`quickstart-cookbook`
 and have a look at the test cases described therein!