Examine source code of Textern

{
  "name": "Textern",
  "description": "Edit text in your favourite external editor!",
  "homepage_url": "https://github.com/jlebon/textern",
  "manifest_version": 2,
  "version": "0.8",
  "browser_specific_settings": {
    "gecko": {
      "id": "textern@jlebon.com",
      "strict_min_version": "57.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "shortcut.js",
        "content.js"
      ]
    }
  ],
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "notifications",
    "nativeMessaging",
    "storage"
  ]
}