Examine source code of copy_url

{
  "manifest_version": 2,
  "name": "copy_url",
  "version": "1.0",
  "description": "Click icon to paste URL to clipboard",
  "icons": {
    "48": "icons/c_48.png"
  },
  "permissions": [
    "tabs",
    "clipboardWrite"
  ],
  "page_action": {
    "default_icon": "icons/c_32.png",
    "default_title": "Copy!",
    "show_matches": [
      "*://*/*"
    ]
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e99244aa-b08a-4162-8188-1eacf38d284b}"
    }
  }
}