[MISC] Outputs for panel button of vgui_screen

[Yankumo-Koishi]

Is your feature request related to a problem? Please describe.

Despite the vgui_screen is functional in Mapbase, it's still kinda un-useable due the lack of outputs for panel buttons

Describe the solution you'd like

As seen in this video

Describe alternatives you've considered

If this is not a good idea, User Outputs can be alternative solutions