Examine source code of Navimacs

{
  "manifest_version": 2,
  "name": "Navimacs",
  "version": "1.3resigned1",
  "description": "WebExtension for Emacs web-page navigation",
  "icons": {
    "48": "icons/emacs_48.png",
    "96": "icons/emacs_96.png"
  },
  "author": "Denis Rechkunov",
  "homepage_url": "https://gitlab.com/pragmader/navimacs",
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "js": [
        "navimacs.js"
      ],
      "matches": [
        "<all_urls>"
      ],
      "all_frames": true,
      "match_about_blank": true
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{882370a4-8962-478e-b0f4-4dfe0b9cc93b}"
    }
  }
}