Add homebrew instructions to install docs

docs/install.rst

@@ -103,6 +103,17 @@ Install from PyPI using pip, preferably into a virtual environment.
 
     pip install --user toot
 
+Homebrew
+--------------------
+
+This works on Mac OSX with `homebrew <https://brew.sh/>`_ installed.
+Tested with on Catalina, Mojave, and High Sierra.
+
+.. code-block:: bash
+
+    brew update
+    brew install toot
+
 Source
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