feat: variable options

[Funaen]

Definition statement of some variable options about monitor: x/y position, the monitor type(normal, big, slider), max/min value.

There are some ideas. What else better syntax?

var slider = 0; # {"type": "slider", "x": 0, "y": 0, "min": 0, "max": 100}

var slider = 0;
%varopt slider {
  type: slider
  x: 0
  y: 0
  min: 0
  max: 100
}

#[var(type="slider", x=0, y=0, min=0, max=100)]
var slider = 0;