Ember-power-select: [Enhancement] Add ability to hide selected options from (multiple select) dropdown

[Glennvd]

In some cases you want to hide the objects that are already added to the selection from your options in the dropdown. This currently can be achieved with the following css rule:

.ember-power-select-multiple-trigger~.ember-view ul>.ember-power-select-option[aria-selected="true"] {
  display:none;
}

However, this seems rather hacky. We maybe should consider an easier way to hide these items.

[cibernox]

This is already doable. I do it all the time actually.

{{#power-select-multiple options=optionsWithoutSelected selected=selected onchange=(actions (mut selected)) as |opt|}}
  {{opt}}
{{/ember-power-select}}

optionsWithoutSelected: computed('options', 'selected', function() {
  return this.get('options').filter((o) => !selected.includes(o));
})