chore(docs): install instructions for macos

docs/install.md

@@ -80,7 +80,20 @@ rm geckodriver-*.tar.gz
     - `which firefox` should return something like `/usr/bin/firefox`
     - `which geckodriver` should return something like `/usr/bin/geckodriver`
 
-#### Windows or MacOS
+#### MacOS
+
+You can use brew to install the geckodriver
+
+```
+brew install geckodriver
+```
+
+It should then be installed at `/usr/local/bin/geckodriver`.
+
+#### Windows
+
+!!! note
+    This tool is not tested under any version of Windows. Consider using an *nix operating system.
 
 - Go to the [geckodriver releases page](https://github.com/mozilla/geckodriver/releases). Find the latest version of the driver for your platform and download it.
 - Extract the archive