Examine source code of Thumb navigation

{
  "description": "Adds overlay navigation icons to page for easier control.",
  "manifest_version": 2,
  "name": "Thumb navigation",
  "version": "1.1resigned1",
  "homepage_url": "https://github.com/AdamVe/thumb-navigation-ext",
  "icons": {
    "48": "icons/thumbnav-48.png"
  },
  "applications": {
    "gecko": {
      "id": "@thumb-navigation-ext",
      "strict_min_version": "57.0"
    }
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_scripts/thumb-navigation.js"
      ]
    }
  ],
  "options_ui": {
    "page": "options/options.html"
  }
}