[Feature Request] Improve usablity with DRM/KMS backend of SDL

[oech3]

easyrpg-player 0.8-2 on AUR work almost noproblem with DRM/KMS backend on Arch Linux.

However, there are some minor problems as below:

1. Full screem mode is forced with any setting.
   One of the idea to solve it is adding 1x or 1x size image on full black screen mode.
2. Unneeded mouse cursor always appear.
3. We need to switch tty to change,unmute system volume and backlight and run external tools such as amixer or brightnessctl
4. Control,Alt+Fn key is commonly used to switch tty. The keybinding conflicts with player's default key config.

Step to run player with DRM\KMS backend:
0. (exporting SDL_VIDEODRVER=kmsdrm is not needed).

1. Add user to input group for keyboard (video,audio may not needed).
2. Run easyrpg-player on getty.