Examine source code of Base64 + AES encoder

{
  "manifest_version": 2,
  "name": "Base64 + AES encoder",
  "version": "1.0.0",
  "description": "",
  "applications": {
    "gecko": {
      "strict_min_version": "58.0",
      "id": "{2d31404b-040d-4505-85fd-1606081c8ad3}"
    }
  },
  "permissions": [
    "storage",
    "activeTab",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background/background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content/crypto-js.min.js",
        "content/content.js"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ],
  "browser_action": {
    "default_popup": "popup/popup.html",
    "default_title": "Base64 + AES encoder",
    "default_icon": "icons/icon-48.png"
  },
  "icons": {
    "48": "icons/icon-48.png"
  }
}