Examine source code of highlight-on-copy

{
  "manifest_version": 2,
  "name": "highlight-on-copy",
  "version": "1.0",
  "description": "Changes selection color for 200ms when you copy text.",
  "permissions": [
    "clipboardWrite",
    "clipboardRead",
    "activeTab",
    "scripting",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "extension.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{284c9212-6871-40fb-895d-63d2b69a0dc1}"
    }
  }
}