Update index.rst

adds a bit of a description to Spice and SpiceyPy to the index page for the docs

docs/index.rst

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 Welcome to SpiceyPy's documentation!
 ====================================
+Introduction
+------------
+
+SpiceyPy is a python wrapper for the `SPICE Toolkit <https://naif.jpl.nasa.gov/naif/>`__.
+SPICE provides access and tools to interact with  planetary and spacecraft ephemeris and ancillary engineering information. 
+Please visit the NAIF website for more details about SPICE.
+
+*IMPORTANT*: I have no current affiliation with NASA, NAIF, or JPL. The
+code is provided "as is", use at your own risk.
+
+Citing SpiceyPy
+---------------
+
+If you are publishing work that uses SpiceyPy, please cite SpiceyPy and the SPICE toolkit.
+SpiceyPy can be cited using the JOSS DOI (`https://doi.org/10.21105/joss.02050`) or with the following:
+
+   Annex et al., (2020). SpiceyPy: a Pythonic Wrapper for the SPICE Toolkit. Journal of Open Source Software, 5(46), 2050, https://doi.org/10.21105/joss.02050
+
+Instructions for how to cite the SPICE Toolkit are available on the NAIF website: 
+
+    https://naif.jpl.nasa.gov/naif/credit.html. 
+
+To cite information about SpiceyPy usage statistics, please cite my 2017 and or 2019 abstracts as appropriate below:
+
+    1. 2017 abstract: `<https://ui.adsabs.harvard.edu/abs/2017LPICo1986.7081A/abstract>`__.
+    2. 2019 abstract: `<https://ui.adsabs.harvard.edu/abs/2019LPICo2151.7043A/abstract>`__.
+
+Documentation Overview
+----------------------
 
 This is the documentation for SpiceyPy. The documentation for each
 function in the wrapper is in large part copied from the "Abstract"