Please add mouse thumb button functionality to go forwards and backwards like in a browser

[Jellyboi420]

I opened the app, logged in, clicked on a library and when I tried to go one step back with the mouse thumb button, nothing happened. Forward also doesn't work.
Could you please add this? Makes navigating quickly with only mouse so much easier because you can keep the cursor centered instead of moving it top left to go back.
Moving one step forward with the forward button is also useful and works in other clients.

[RadicalMuffinMan]

moved to #104