Examine source code of ePorezna Extension

{
  "manifest_version": 2,
  "name": "ePorezna_new",
  "version": "1.4",
  "browser_specific_settings": {
    "gecko": {
      "id": "firefoxextension12@porezna-uprava.hr",
      "strict_min_version": "58.0"
    }
  },
  "description": "Dodatak za rad sa sustavom ePorezna.",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.teched.hr/*",
        "*://localhost/*",
        "*://*.apis-it.local/*",
        "*://*.porezna-uprava.hr/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "page.js"
  ],
  "permissions": [
    "nativeMessaging"
  ]
}