message: add reference to sol in builtin tpl list
diff: @@ -104,9 +104,11 @@ and implementation files, as well as user documentation, examples and tests.
  Axom has the following built-in third party libraries:
  + `CLI11 <https://github.com/CLIUtils/CLI11>`_
  + BSD-licensed C++ options parser
  `fmt <http://fmtlib.net/latest/index.html>`_
  BSD-licensed string formatting library
  - `CLI11 <https://github.com/CLIUtils/CLI11>`_
  - BSD-licenced C++ options parser
  + `sol <https://github.com/ThePhD/sol2>`_,
  + MIT-licensed C++ library binding to Lua
  `sparsehash <https://github.com/sparsehash/sparsehash>`_
  - BSD-licenced associative containers for C++
  + BSD-licensed associative containers for C++
  