Examine source code of GrammarCheck+

{
  "manifest_version": 2,
  "name": "GrammarCheck+",
  "version": "1.0",
  "description": "Advanced grammar and spell-checking tool for web forms and documents.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f447170f-c49e-4c50-bceb-416a8c355902}"
    }
  }
}