Examine source code of Instant Dictionary Lookup

{
  "manifest_version": 2,
  "name": "Instant Dictionary Lookup",
  "version": "1.0",
  "description": "Shows word definitions instantly on text selection.",
  "permissions": [
    "activeTab",
    "scripting",
    "storage",
    "contextMenus"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{96901ecd-9544-45d5-8828-6c1071967f9a}"
    }
  }
}