Examine source code of Cambridge Dictionary

{
  "manifest_version": 2,
  "name": "Cambridge Dictionary",
  "description": "Searches highlighted text on Cambridge Dictionary",
  "version": "2.0",
  "icons": {
    "48": "icons/dictionary.png",
    "96": "icons/dictionary.png"
  },
  "permissions": [
    "contextMenus"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "sidebar_action": {
    "default_panel": "/index.html",
    "open_at_install": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{16c81fda-3ecf-496d-a9c6-7865544962fd}"
    }
  }
}