Examine source code of peek

{
  "manifest_version": 2,
  "name": "peek",
  "version": "1.0",
  "description": "look up words",
  "icons": {
    "192": "logo192.png",
    "512": "logo512.png"
  },
  "browser_action": {
    "default_icon": "logo192.png",
    "default_title": "peek",
    "default_popup": "index.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{12ae30d6-052a-4ded-a634-d25590e92e07}"
    }
  }
}