message: modifiers/snapSize: use utils.is.function
diff: @@ -50,7 +50,7 @@ const snapSize = {
  for (const snapTarget of options.targets) {
  let target;
  - if (utils.isFunction(snapTarget)) {
  + if (utils.is.function(snapTarget)) {
  target = snapTarget(relativeX, relativeY, interaction);
  }
  else {
  