updated add_remove.svx by adding reducer to function add that sets item responsiveness

[frantic0]

for all layout column configurations

e.g.

if you have

  let cols = [
    [2880, 12],
    [1600, 12],
    [1280, 8], // over this rez is failling
    [1024, 6],
    [800, 3],
    [500, 2]
  ];

sets all COL props to the new item to add