Examine source code of Jisho.org Context Menu

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "version": "1.0",
  "default_locale": "en",
  "applications": {
    "gecko": {
      "strict_min_version": "56.0a1"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "menus",
    "activeTab"
  ],
  "icons": {
    "16": "icons/page-16.png",
    "32": "icons/page-32.png",
    "48": "icons/page-48.png"
  }
}