[Request] Add a launch option for HiDPI Scaling

[Astilex5]

Hi.

As the title suggests I would like to propose the idea of adding a toggle option in LSI settings to use this:

GDK_SCALE=2x lsi-steam

Reason: Currently steam is almost unusable on HiDPI displays as the font and UI is very small as Valve has neglected 3K and 4K scaling for a while with no solution in sight.

I would like to see this as an option as it would really set LSI apart from regular Steam, while it being a big help to the gaming community at the same time.

If there is a lack of man/woman power I could make changes and PR, but I am not really familiar with the code and how it works.

Regards,
Chris