add cross reference

This table lists the supported names, their data types, length of the

data area, and a short description.  The ``bigint`` type may be defined

to be either an ``int`` or an ``int64_t``.  This is selected at

:ref:`compile time <size>`.

:ref:`compile time <size>` and can be queried through calling

:cpp:func:`lammps_extract_setting`.

.. list-table::

   :header-rows: 1