Update doc/index.rst
Complete information on index.rst of user guide (the first page of the home page) along the lines of hiphive
and `icet.
:program:`dynasor` requires Python (or Python3) and invokes functionality from
...
:program:`dynasor` and its development are hosted on `gitlab
<https://gitlab.com/materials-modeling/dynasor>`_. Bugs and feature
requests are ideally submitted via the `gitlab issue tracker
<https://gitlab.com/materials-modeling/dynasor/issues>`_. The development
team can also be reached by email via dynasor@materialsmodeling.org.