Examine source code of SuperKopilka-plus

{
  "manifest_version": 2,
  "name": "SuperKopilka+",
  "version": "1.1",
  "description": "Adds useful functionality to SuperKopilka Calculator",
  "default_locale": "en",
  "icons": {
    "48": "icons/skPlus-logo-48px.png",
    "96": "icons/skPlus-logo-96px.png"
  },
  "applications": {
    "gecko": {
      "id": "oster.ok@gmail.com"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://calc.superkopilka.com/save.php*"
      ],
      "js": [
        "js/calculator/extend.js"
      ]
    }
  ]
}