create shadow secondary service-worker

[Akravish]

Build includes files background.js, content.js in the modal window. When you click on the extension icon, a second service worker connected to index.html is launched.

  <script defer="defer" src="/static/js/main.js"></script>
  <script defer="defer" src="/static/js/background.js"></script>
  <script defer="defer" src="/static/js/content.js"></script>

[pogzyb]

@Akravish Did you figure out a way to resolve this behaviour? I'm experiencing it with something I built using this repo. I'm not as experienced with frontend development, so not sure if the snippet you included is the solution or what is causing the problem. Thanks in advance!