window.external.AddSearchProvider 참고자료

• https://stackoverflow.com/questions/41281475/chrome-does-not-support-adding-searchengine-through-javascript-window-external

• https://developer.mozilla.org/en-US/docs/Web/API/Window/sidebar/Adding_search_engines_from_Web_pages

• http://help.dottoro.com/ljcmlman.php

• https://bugs.chromium.org/p/chromium/issues/detail?id=100495

• https://www.makeuseof.com/tag/3-ways-to-enhance-google-chromes-custom-search/

• https://2ality.com/2011/01/browser-keywords-using-address-bar-as.html

• https://2ality.com/2013/06/chrome-omnibox-search.html

• https://stackoverflow.com/questions/21605933/add-a-custom-search-engine-via-javascript