async activate(opts, payload) {
    return undefined;
  }
Activates the plugin.
@param {!{
  adapter: !Adapter,
  $sidebar: !JQuery,
  $toggler: !JQuery,
  $views: !JQuery,
  treeView: !TreeView,
  optsView: !OptionsView,
  errorView: !ErrorView,
}}

@param {{
 state: UserState,
}}

@return {!Promise<undefined>}