A chrome extension can inject script into the page, this is called content script.

https://developer.chrome.com/extensions/getstarted
https://developer.chrome.com/extensions/content_scripts
https://developer.chrome.com/extensions/messaging

图标变灰的问题

Add browseraction.defaulticon in your manifest.json file

{
  ...

  "browser_action": {
    "default_icon": "icons/icon-32.png";
  },

  ...
}

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