Examine source code of SnapSaver

{
  "manifest_version": 2,
  "name": "SnapSaver",
  "version": "1.0",
  "description": "Capture and save website screenshots even when offline.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{206d8f04-e408-4fe1-9f28-4d4f9dd5ee96}"
    }
  }
}