Examine source code of Word Check List

{
  "manifest_version": 2,
  "name": "Word Check List",
  "version": "1.0",
  "description": "Define up to 5 watch words/phrases, scan pages, highlight matches, and navigate through them.",
  "browser_specific_settings": {
    "gecko": {
      "id": "word-check-list@danielschwartz",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "icons": {
    "48": "icon-48.png",
    "96": "icon-96.png"
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Word Check List",
    "default_icon": {
      "48": "icon-48.png",
      "96": "icon-96.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ]
}