Examine source code of Contrast Checker Popup

{
  "manifest_version": 2,
  "name": "Contrast Checker Popup",
  "version": "1.0",
  "description": "Quickly calculate contrast ratio between two HEX colors in a popup.",
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png",
    "default_title": "Contrast Checker"
  },
  "permissions": [],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{663e36ec-fd0c-40f6-b014-d86d366517ae}"
    }
  }
}