Add option to launch on integrated GPU on linux

[Stanko2]

Check for existing issues

• Completed

Describe the feature

Make zed able to use non-discrete GPU on Linux for rendering to reduce battery usage. It could be added as an option, or it could use discrete GPU only if there is another process running on it. So that the GPU wouldn't start because of zed.

If applicable, add mockups / screenshots to help present your vision of the feature

At least for Nvidia, check nvidia-smi on startup. If there is another process using the GPU, zed should use it also. If not use integrated graphics to prevent battery drain.

Another option could be to set the GPU manually in settings.