Examine source code of Wiktionarek

{
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "52.0",
      "id": "{8a51f0da-ca02-4644-a540-95ef21d5d6c9}"
    }
  },
  "browser_action": {
    "default_icon": "icons/wiktionarek-32.png",
    "default_title": "Wiktionarek"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "word-processor.js",
        "frame-trimmer.js",
        "frame-builder.js",
        "frame-init.js"
      ],
      "all_frames": true
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "description": "Look up a word on Wiktionary with your customized layout just by clicking.",
  "icons": {
    "32": "icons/wiktionarek-32.png",
    "48": "icons/wiktionarek-48.png",
    "96": "icons/wiktionarek-96.png"
  },
  "manifest_version": 2,
  "name": "Wiktionarek",
  "options_ui": {
    "page": "options/options.html"
  },
  "permissions": [
    "webNavigation",
    "storage",
    "contextMenus",
    "activeTab",
    "https://en.wiktionary.org/api/rest_v1/page/html/*"
  ],
  "version": "0.2"
}