Examine source code of Grayscale Toggle v2

{
  "manifest_version": 2,
  "name": "Grayscale Toggle",
  "version": "1.0",
  "description": "Toggle grayscale on any webpage for a comfortable reading experience.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/grayscale-48.png",
    "default_popup": "popup.html",
    "default_title": "Toggle Grayscale"
  },
  "icons": {
    "48": "icons/grayscale-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{80111509-2f4f-4d05-8fa1-28f2e15e9210}"
    }
  }
}