addOrCreateList = (container, key, x) => {
  if (container[key]) {
    if (container[key].length) container[key].push(x);
    else container[key] = [container[key], x];
  } else container[key] = [x];
}
Add to List or Create List (container)
@param {object} container
@param {string} key
@param {object} x
@returns {void}