Examine source code of RRSign

{
  "name": "RRSign",
  "version": "1.5",
  "manifest_version": 2,
  "description": "RRSign.",
  "icons": {
    "123": "icons/logo_RRSIGN.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "rrsign@rrsign.com"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.rrdocs.com.br/*",
        "https://*.rrsign.com.br/*"
      ],
      "run_at": "document_start",
      "js": [
        "jquery-3.5.1/jquery-3.5.1.min.js",
        "inject.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "icons/logo_RRSIGN.png",
    "default_title": "RRSign",
    "default_popup": "main.html"
  },
  "externally_connectable": {
    "matches": [
      "https://*.rrdocs.com.br/*",
      "https://*.rrsign.com.br/*"
    ]
  },
  "web_accessible_resources": [
    "script.js",
    "main.js"
  ],
  "permissions": [
    "https://*.rrdocs.com.br/*",
    "https://*.rrsign.com.br/*",
    "tabs",
    "nativeMessaging"
  ]
}