Examine source code of osu pp calculator

{
  "manifest_version": 2,
  "name": "pp calculator",
  "description": "Calculates the osu! pp values directly in your web browser",
  "version": "1.4.0",
  "icons": {
    "128": "icons/icon_128.png"
  },
  "permissions": [
    "storage",
    "tabs",
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_title": "pp calculator",
    "default_popup": "popup.html",
    "default_icon": {
      "128": "icons/icon_128.png"
    }
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "content_security_policy": "script-src 'self'; object-src 'self';",
  "browser_specific_settings": {
    "gecko": {
      "id": "pp-calculator@example.com",
      "strict_min_version": "91.0"
    }
  }
}