fix the sliders changing only one value

glsl/sliders.js

        }
        
        slider.onChange = function(ev, i) {
          slider.values[0] = parseFloat(ev.target.value);
          slider.values[i] = parseFloat(ev.target.value);
          if (slider.type == "vec2") {
            gl.uniform2f(slider.uniform, slider.values[0], slider.values[1]);
          } else if (slider.type == "vec3") {