With your help I’ve developed this addon, you can see here my code including the manifest file:
https://github.com/log69/yesscript2
I can do anything from the content script (foreground) but cannot do anything from the background. I cannot debug or test anything like this unfortunately. Thanks for your help anyway.
I’m reading this page now but doesn’t help so far:
https://stackoverflow.com/questions/3829150/google-chrome-extension-console-log-from-background-page
I’m still looking for answers.