Examine source code of Common Mistakes Spotter

{
  "manifest_version": 2,
  "name": "Common Mistakes Spotter",
  "version": "1.0",
  "description": "Detect common grammar errors on web pages.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{eb8d7dda-bbf1-4091-858a-37cb5af08806}"
    }
  }
}