[Container] Add silent parameter to add() method

The Neo.container.Base.add(item) method currently does not support a silent parameter, unlike insert(index, item, silent) and remove(component, destroy, silent).

This limitation forces a VDOM update cycle every time add() is called, which is inefficient when adding multiple items sequentially or when managing complex state transitions (like in drag-and-drop operations) where we might want to defer the update.

Task: Update Neo.container.Base.prototype.add to accept a silent parameter and pass it through to insert.

    /**
     * Inserts an item or array of items at the last index
     * @param {Object|Array} item
     * @param {Boolean} [silent=false]
     * @returns {Neo.component.Base|Neo.component.Base[]}
     */
    add(item, silent=false) {
        let me = this;
        return me.insert(me.items ? me.items.length : 0, item, silent)
    }