[docs] Added conda

doc/usage.rst

@@ -103,7 +103,14 @@ the previous section. Then compile the ``doc`` target/project, for example::
   make doc
 
 This will generate the HTML documentation in ``doc/html``.
-  
+
+Conda
+=====
+
+fmt can be install (for Windows, macOS and Linux) on `Conda <https://docs.conda.io/en/latest/>`__, using its `conda-forge <https://conda-forge.org>`__ `package <https://github.com/conda-forge/fmt-feedstock>`__, as follows::
+
+  conda install -c conda-forge fmt
+
 Android NDK
 ===========