README: Update features and add CMake compilation steps.

Signed-off-by: Grzegorz Kowal <grzegorz@amuncode.org>

README.md

@@ -22,9 +22,11 @@ following features are already implemented:
 * viscous and resistive source terms,
 * support for passive scalars (up to 100),
 * data stored in internal XML+binary or HDF5 format,
+* support for Zstandard, LZ4, and LZMA compression in XML+binary format,
 * Python interface to read snapshots in both formats,
 * MPI parallelization,
-* completely written in Fortran 2003,
+* completely written in Fortran 2008,
+* simple Makefile or CMake for executable building,
 * minimum requirements, only Fortran compiler and Python are required to
   prepare, run, and analyze your simulations.
 
@@ -62,6 +64,8 @@ Requirements
   with version 1.10 or newer. The code now uses the new XML-binary snapshot
   format. However, if you still want to use older HDF5 snapshot format, you
   will need these libraries.
+* Optional [CMake](https://cmake.org) version 3.16 or newer, for managing the
+  build process.
 
 
 Environment Variables
@@ -73,8 +77,29 @@ variable _HDF5DIR_ is set in your **~/.bashrc** (or **~/.cshrc**) and pointing
 to the location where the HDF5 libraries have been installed.
 
 
-Compilation
-===========
+Recommended compilation (using CMake)
+=====================================
+
+1. Clone the AMUN source code:
+  - from Bitbucket:
+    `git clone https://grzegorz_kowal@bitbucket.org/amunteam/amun-code.git`,
+  - from GitLab:
+    `git clone https://gitlab.com/gkowal/amun-code.git`
+  - or unpack the archive downloaded from page
+   [Downloads](https://bitbucket.org/amunteam/amun-code/downloads/).
+2. Create a directory for compilation in any location,
+   e.g. `mkdir cmake-build && cmake-build`.
+3. Call `ccmake <path to amun-code>`, e.g. `ccmake ..`, and press 'c' once.
+   Configure available options. Press 'c' once again, and 'g' to
+   generate makefiles. Alternatively, just call `ccmake <path to amun-code>`
+   for default options.
+4. Compile the code using `make`. The executable file **amun.x** should be
+   created.
+
+
+Alternative compilation (using `make.conf`)
+===========================================
+
 1. Clone the AMUN source code:
   - from Bitbucket:
     `git clone https://grzegorz_kowal@bitbucket.org/amunteam/amun-code.git`,