Support of XF86 Keybinds

[pharuxtan]

Is your feature request related to a problem? Please describe.
I tried to use XF86 keybinds to control brightness through the keyboard, but when i included the header <X11/XF86keysym.h> in the structs.h and then added XF86XK_MonBrightnessUp/XF86XK_MonBrightnessDown with custom keybinds, it just didn't worked.

Describe the solution you'd like
Custom keybinds commands to fire when XF86 keybinds are used.

Describe alternatives you've considered
I didn't considered any alternative.

Additional context
No additional context