Examine source code of J Caesar Cipher

{
  "manifest_version": 2,
  "name": "J Caesar Cipher",
  "version": "0.1",
  "description": "Encrypt and decrypt text using Caesar Cipher shift",
  "icons": {
    "16": "images/jcc-16.png",
    "32": "images/jcc-32.png",
    "48": "images/jcc-48.png",
    "64": "images/jcc-64.png"
  },
  "sidebar_action": {
    "default_icon": {
      "16": "images/jcc-16.png",
      "32": "images/jcc-32.png",
      "48": "images/jcc-48.png",
      "64": "images/jcc-64.png"
    },
    "default_title": "J Caesar Cipher",
    "default_panel": "caesarCipher.html"
  },
  "permissions": [
    "storage",
    "clipboardWrite",
    "notifications"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{511f02cc-ceaa-45ec-b29b-f16ccdaf0f24}"
    }
  }
}