Correct spelling and add sections

This commit corrects some spelling and grammar and adds some sections:

* Support
* Contributing - Building the docs
* CSEM ModEM Version
* Spherical ModEM Version

Author: MiCurry

docs/source/contributing.rst

@@ -0,0 +1,60 @@
+Contributing
+=========================
+
+Users are welcome to contribute to ModEM and we welcome contributions! 
+
+We highly recommend opening a GitHub Issue first so that new contributions can be
+discussed with ModEM authors, especially for large pull requests.
+
+Contributions can be made via a `GitHub pull request <_github_pr>`_ at the ModEM
+repository: https://github.com/magnetotellurics/ModEM/compare.
+
+.. _github_pr: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests
+
+Steps To Open a Pull Request (PR)
+----------------------------------
+
+See: `Contributing to a project`_.
+
+.. _Contributing to a project : https://docs.github.com/en/get-started/exploring-projects-on-github/contributing-to-a-project
+
+Tips & Testing
+---------------
+
+* Please keep pull requests to reasonable sizes (consider breaking up large PR's
+  into small ones)
+* If you able, please test your changes using both the GNU gfortran compiler and
+  Intel ifort repository (but Gfortran at the minimum if you don't have access
+  to Intel).
+* Contribute any relative documentation to this Documentation (See
+  :ref:`building-the-docs`)
+* Run the unit tests in the ``unit_testing`` directory (Currently not added)
+
+.. _building-the-docs:
+
+Building this Documentation
+----------------------------
+
+This `Sphinx <_sphinx_page>`_ documentation can easily be built if you have Sphinx installed. If you
+have Python and Pip installed, you can install Sphinx by:
+
+.. code-block:: bash
+
+    $ pip install -U sphinx
+
+For more information on installing Sphinx see: https://www.sphinx-doc.org/en/master/usage/installation.html.
+
+After making changes to the documentation, you can build locally for testing by doing the following:
+
+.. code-block:: bash
+
+    $ cd ModEM/docs
+    $ make html
+
+The HTML files will be built in ``ModEM/docs/build``. You can open these locally
+and view them and ensure they look correct. You do not need to (and will not be
+able to) commit the built HTML files.
+
+If you change the documentation, please ensure that it builds without errors.
+
+.. _sphinx_page: https://www.sphinx-doc.org/en/master/

docs/source/csem_modem.rst

@@ -0,0 +1,65 @@
+CSEM Version of ModEM
+----------------------
+
+.. warning::
+
+   The CSEM version of ModEM is not fully validated and has only been used in
+   some instances. We cannot guarantee correct or accurately results with it.
+
+Please see the warning above. The CSEM version is really not yet ready for
+production, but we are providing it here for future development and testing.
+
+The CSEM version of ModEM is available on the ``CSEM`` branch of ModEM:
+
+.. code-block:: bash
+
+   $ git checkout CSEM
+
+The CSEM version requires one of two submodules that are not apart of ModEM:
+
+* Dipole1D - Apart of OCCAM1DCSEM - `provided by SCRIPPS <_dipole1d>`_.
+* EM1D - Provided by Rita Streich's - But not yet avaliable for public release.
+
+For more information on the CSEM version of ModEM see the README on the CSEM
+branch: https://github.com/magnetotellurics/ModEM/blob/CSEM/README.md
+
+.. _dipole1d: https://marineemlab.ucsd.edu/Projects/Occam/1DCSEM/
+
+
+Configuring and Compiling with Dipole1D
+----------------------------------------
+
+The license associated with Dipole1D disallows us from including it in our
+source code; however, the configure script (``/f90/CONFIG/configure``)
+contains code to automatically retrieve it for you. The configure script has
+the following options:
+
+.. code-block:: bash
+
+   $ cd ModEM/f90/
+   $ ./CONFIG/configure 
+    Usage: ./CONFIG/Configure with the following options:
+    Compiler: Choose from supported compilers: [ gfortran | ifort ]
+    Makefile: Provide a name for your output Makefile name.
+    [Debug or Release]: Choose whether you want to compile the Debug or Release version.
+    [MPI or Serial]:  Choose whether you want to compile the parallel (MPI) or serial version.
+    [MF or SP or SP2]:  Choose between the Matrix Free (MF), or the Modified System of Eqs 1 (SP), or the Modified System of Eqs 2 (SP2) of the code.
+    [MT or MT+CSEM]:  Compile MT or MT+CSEM. In Case of MT+CSEM, choose in the following option whether Dipole1D or EM1D or both will be used to get for the secondary field formulation.
+    [Dipole1D or EM1D]:  (Optional) - Choose whether you have Dipole1D, or EM1D in the source files folder '/3D_MT/CSEM_module'
+
+To configure with Dipole1D run:
+
+.. code-block:: bash
+
+   $ cd ModEM/f90
+   $ ./CONFIG/configure ./CONFIG/Configure gfortran Makefile Release MPI MF MT+CSEM Dipole1D
+    Dipole1D is not currently in ./3D_MT/CSEM_module/Dipole1D
+    Would you like to have this script automatically download it now? [Yes/No]
+
+You will be presented with the above prompt, type 'Yes' to automatically
+download Dipole1D, then you'll be able to type ``make`` to compile:
+
+.. code-block:: bash
+
+   $ make
+