Article updated for v2.0.1.
By going to the app settings, in the "Advance section, you can find a field where you can place it. The same happens with CSS code, specially used to change the user interface of the app.
For instance, some users want to reload the app every X time because the app they are using get disconnected by inactivity. Here's an example, to Auto-Refresh every 10 minutes.
setInterval(() => location.reload(), 600000);