Examine source code of Signet

{
  "manifest_version": 2,
  "name": "Signet",
  "author": "Hax0rbana",
  "version": "0.1.3",
  "browser_action": {
    "default_icon": {
      "32": "icons/icon-32.png",
      "64": "icons/icon-64.png",
      "128": "icons/icon-128.png"
    },
    "default_title": "Signet",
    "default_popup": "popup.html"
  },
  "permissions": [
    "webNavigation",
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "all_frames": true,
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_idle",
      "js": [
        "content-scripts/autofill.js"
      ]
    }
  ],
  "icons": {
    "32": "icons/icon-32.png",
    "64": "icons/icon-64.png",
    "128": "icons/icon-128.png"
  },
  "applications": {
    "gecko": {
      "strict_min_version": "59.0",
      "id": "{cac36781-9067-4f2a-93b7-a7380c1ab1a8}"
    }
  },
  "commands": {
    "login": {
      "suggested_key": {
        "default": "Ctrl+Shift+L"
      },
      "description": "Login to current webpage"
    }
  }
}