add sphinx source for cpp_fort_and_py example (#736)

src/docs/sphinx/tutorial_cpp_fort_and_py.rst

@@ -0,0 +1,37 @@
+.. # Copyright (c) Lawrence Livermore National Security, LLC and other Conduit
+.. # Project developers. See top-level LICENSE AND COPYRIGHT files for dates and
+.. # other details. No copyright assignment is required to contribute to Conduit.
+
+=======================================================
+Passing Conduit Nodes between C++, Fortran, and Python
+=======================================================
+
+The ``cpp_fort_and_py`` example demonstrates how to pass Conduit Nodes between
+C++, Fortran, and Python. It is a standalone example that you can build with
+CMake against your Conduit install.
+
+You can find this example under ``src/examples/cpp_fort_and_py`` in
+Conduit's source tree, or under ``examples/conduit/cpp_fort_and_py`` in
+a Conduit install.
+
+It includes source for an embedded python interpreter and also shows how
+to create a Fortran module that binds Conduit Nodes via Conduit's C-API.
+
+It creates two executables:
+
+ ============================ ===========================================
+  **conduit_cpp_and_py_ex**    Demo of C++ to Python and vice versa
+  **conduit_fort_and_py_ex**   Demo of Fortran to Python and vice versa
+ ============================ ===========================================
+
+This demos wrapping Conduit Nodes, effectively creating referenced
+data across languages. You can also use `set_external` to directly access
+and change zero-copied data.
+
+Please see the main CMakeList.txt file for details on building and running:
+
+``cpp_fort_and_py/CMakeLists.txt`` excerpt:
+
+.. literalinclude:: ../../examples/cpp_fort_and_py/CMakeLists.txt
+   :lines: 6-34
+   :dedent: 2