Feature Request: change display resolution when toggling activation state

[emansom]

Is your feature request related to a problem? Please describe. Low-end graphics cards usually can only handle lower resolutions at an acceptable frame rate.

Currently, there's no mechanism in GameMode to let it change resolution to e.g. 720p when activated.

Describe the solution you'd like GameMode supporting an optional setting to configure what resolution to change the primary display to, similar to how this is implemented in Lutris.