Examine source code of TJRS Signer

{
  "name": "TJRS Signer",
  "version": "0.8.2",
  "author": "Tribunal de Justiça do Rio Grande do Sul",
  "description": "Assinador A3 ICP-Brasil do TJRS",
  "manifest_version": 2,
  "applications": {
    "gecko": {
      "id": "tjrssigner@tjrs.jus.br",
      "strict_min_version": "55.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.tjrs.gov.br/*",
        "*://*.tjrs.jus.br/*",
        "*://localhost/*"
      ],
      "js": [
        "signer-inject.js"
      ],
      "all_frames": true
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "icons": {
    "128": "sign-icon.png"
  },
  "permissions": [
    "nativeMessaging"
  ]
}