MPI is now optional (#19) [skip ci] (#21)

README.md

@@ -55,9 +55,9 @@ Phenomena [(SPEC)](https://spec.labworks.org/home) Center.
 * CMake (3.14+)
 * BLAS / LAPACK
 * [BLAS++](https://github.com/icl-utk-edu/blaspp) / [LAPACK++](https://github.com/icl-utk-edu/lapackpp)
-* MPI 
 * [`std::mdspan`](https://en.cppreference.com/w/cpp/container/mdspan) with [Kokkos](https://github.com/kokkos/mdspan) extensions
 * spdlog
+* MPI (Optional)
 * OpenMP (Optional)
 * Boost (Optional)
 * Catch2 (Testing)
@@ -122,6 +122,7 @@ target_link_libraries( my_target PUBLIC macis::macis )
 | Variable Name              | Description                                               | Default  |
 |----------------------------|-----------------------------------------------------------|----------|
 | `MACIS_ENABLE_OPENMP`      | Enable OpenMP Bindings                                    |  `ON`    |
+| `MACIS_ENABLE_MPI`         | Enable MPI Bindings                                       |  `ON`    |
 | `MACIS_ENABLE_BOOST`       | Enable Boost Bindings                                     |  `ON`    |
 | `BLAS_LIBRARIES`           | Full BLAS linker.                                         |  --      |
 | `LAPACK_LIBRARIES`         | Full LAPACK linker.                                       |  --      |