DOC: More info on landing page

doc/index.rst

@@ -4,7 +4,23 @@
 
 
 The ``fslpy`` package is a collection of utilities and data abstractions used
-by |fsleyes_apidoc|_.
+within `FSL <https://fsl.fmrib.ox.ac.uk/fsl/fslwiki>`_ and by
+|fsleyes_apidoc|_.
+
+
+The top-level Python package for ``fslpy`` is called ``fsl``.  It is broadly
+split into the following sub-packages:
+
+
+.. autosummary::
+
+   fsl.data
+   fsl.utils
+   fsl.scripts
+   fsl.transform
+   fsl.version
+   fsl.wrappers
+
 
 .. toctree::
    :hidden: