addCorePlugins() {
    this.loader.corePlugins.forEach((Plugin) => {
      const plugin = new Plugin(this.core)
      this.core.addPlugin(plugin)
      this.setupExternalInterface(plugin)
    })
    return this.core
  }
given the core plugins (`loader.corePlugins`) it builds each one
@method addCorePlugins
@return {Core} the core with all plugins