slotComponent (type, slot) {
    const def = this.options.library[type]
    if (def && def.slotComponents && def.slotComponents[slot]) {
      return def.slotComponents[slot]
    }
    return this.options.slotComponents[slot]
  }
What component should be rendered for the given slot location and type.
@param {string} type the type of component
@param {string} slot the name of the slot