docs: Update README.md

Author: kxxt

README.md

@@ -27,6 +27,8 @@ In order to render the math in many different fonts we use  XeLaTeX, generate a
 
 Thanks to [@katie-lim](https://github.com/katie-lim), you can use a nice user interface as a quick way to get the model prediction. Just call the GUI with `python gui.py`. From here you can take a screenshot and the predicted latex code is rendered using [MathJax](https://www.mathjax.org/) and copied to your clipboard.
 
+Under linux, it is possible to use `gui.py` with `gnome-screenshot` which comes with multiple monitor support. You just need to run `python gui.py --gnome` (**Note: ** you should install `gnome-screenshot` beforehand).
+
 ![demo](https://user-images.githubusercontent.com/55287601/117812740-77b7b780-b262-11eb-81f6-fc19766ae2ae.gif)
 
 If the model is unsure about the what's in the image it might output a different prediction every time you click "Retry". With the `temperature` parameter you can control this behavior (low temperature will produce the same result).