Add the ability to change internal resolution of emulated games

[Tau5]

I have a 720 display and steam-buddy configures on the fly retroarch cores to render at 1080.
My PC struggles in some games to render at a such high resolution ane changing the resolution to a lower one could improve the experience.
This modification could be made by adding an option in the settings menu or even just moving the configuration files to the home directory

[alkazar]

Sorry to hear that the updated default configuration doesn't work well for you.
I have added a section to the Steam Buddy README with information on how to change the configuration here:
https://github.com/gamer-os/steam-buddy/blob/master/README.md#configuration

One possible solution is to have a few different sets of default configurations aimed at different resolutions and either be able to have the user change that manually or automatically by detecting the current resolution.

[Tau5]

Thanks! I didn't know about that feature!
I think selecting it manually would be better for people with custom resolutions